Guinness Brownies with Irish Cream Frosting (Fudgy St. Patrick’s Day Dessert!)
Get ready to wow everyone this St. Patrick's Day with the most decadent brownies you've ever tasted! These Guinness Brownies are rich, fudgy, and intensely chocolatey-and the best part? You won't taste any beer at all. The stout simply adds incredible moisture and a deeper, more complex chocolate flavor that takes a regular brownie to the next level.
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Topped with a silky Irish cream frosting that's just the right amount of boozy, these brownies are an adults-only treat that's completely approachable for any home baker. As a nurse and mom, I love recipes that feel special without being complicated-and these Guinness Brownies deliver on both flavor and wow factor. Fair warning: these disappear fast!
Why You’ll Love These Guinness Brownies
- Incredibly fudgy: The Guinness adds extra moisture, creating the densest, most fudgy brownie texture you've ever had.
- No beer taste: The baking process transforms the stout-you get deeper chocolate flavor without any beer aftertaste. Even people who don't like beer love these!
- Showstopping frosting: The Bailey's Irish Cream frosting is silky, slightly boozy, and absolutely irresistible.
- Simple ingredients: No fancy techniques required-if you can melt butter and stir, you can make these brownies.
- Make-ahead friendly: Bake the brownies ahead of time and frost closer to your St. Patrick's Day celebration.
- Customizable: Adjust the Bailey's in the frosting from subtle to strong, or make a completely non-alcoholic version.
Ingredient Notes
Brownie ingredients:
- Unsalted Butter (1 cup/2 sticks): Provides richness and that melt-in-your-mouth fudgy texture. Unsalted lets you control the salt level.
- Granulated Sugar (1¼ cups): Sweetens the batter and balances the slight bitterness of the stout and cocoa.
- Guinness Stout (¾ cup): The star ingredient! Any dark stout works, but classic Guinness Draught is my go-to. Don't worry-you won't taste beer in the finished brownies, just richer, more complex chocolate flavor.
- Pure Vanilla Extract (2 teaspoons): Enhances the chocolate and rounds out all the flavors.
- Eggs (2 large): Room temperature eggs incorporate more smoothly and create a better texture.
- Dutch-Process Cocoa Powder or Unsweetened Cocoa Powder (¾ cup): Dutch-process cocoa has a smoother, less acidic flavor that pairs beautifully with the stout. This is a generous amount-it's what makes these brownies so intensely chocolatey!
- All-Purpose Flour (1 cup): Measured correctly using the spoon-and-level method for consistent results.
- Fine Sea Salt (¼ teaspoon): A small amount goes a long way in bringing out the chocolate flavor.
- Semi-Sweet Chocolate Chips (½ cup, optional): Adds pockets of melty chocolate throughout. Totally optional, but highly recommended!
For the Irish Cream Frosting:
- Unsalted Butter (½ cup/1 stick): Must be softened to room temperature for a smooth, fluffy frosting.
- Powdered Sugar (3 cups): Sift it first to avoid lumps! This creates that smooth, sweet base for the frosting.
- Bailey's Irish Cream (2-3 tablespoons): Start with 2 tablespoons for a subtle flavor, or go with 3 for a stronger Irish cream taste. You can also substitute Irish cream-flavored coffee creamer for a non-alcoholic version.
- Pure Vanilla Extract (1 teaspoon): Adds warmth and depth to the frosting.
- Heavy Cream (1-2 tablespoons, if needed): Only add this if your frosting is too thick-it loosens the consistency beautifully.
Garnishes (Optional):
- Chocolate shavings or cocoa powder for dusting
- Gold sprinkles or sanding sugar
- Green sanding sugar
- St. Patrick's Day themed sprinkles
How to Make Guinness Brownies with Irish Cream Frosting
Make the Brownies
Step 1: Prep your pan. Preheat your oven to 350°F with the rack in the center position. Line a 9x9-inch baking pan with parchment paper, leaving overhang on two sides for easy removal. Lightly grease the parchment with butter or non-stick spray.
Step 2: Melt butter, then add sugar and cocoa. In a medium saucepan, melt the butter over medium heat. Remove from heat and whisk in the sugar until combined. Add the cocoa powder and whisk until smooth and glossy-it will look like the richest chocolate sauce you've ever seen!
Step 3: Add the Guinness. Pour in the Guinness and whisk until combined. It will foam up slightly-this is totally normal! The mixture will smell incredible.
Step 4: Add eggs and vanilla. Let the mixture cool for about 5 minutes (you don't want to scramble the eggs!). Whisk in the vanilla extract, then add the eggs one at a time, whisking well after each addition until the batter is smooth.
Step 5: Add dry ingredients. Add the flour and salt directly to the saucepan. Using a spatula or wooden spoon, stir until just combined-do not overmix. Overmixing develops gluten and creates tough brownies, so stir just until no flour streaks remain. Fold in the chocolate chips if using.
Step 6: Bake. Pour the batter into the prepared pan and spread evenly. Bake for 35-40 minutes, until the top is set and slightly crackled, and a toothpick inserted in the center comes out with moist crumbs (not wet batter). For fudgier brownies, pull them at 35 minutes. The brownies will continue to set as they cool.
Step 7: Cool completely. Let the brownies cool in the pan on a wire rack for at least 1 hour before frosting. I know it's tempting to dive in, but patience pays off! For cleaner cuts, refrigerate for 30 minutes after cooling.
Make the Irish Cream Frosting
Step 8: Beat the butter. In a large bowl, beat the softened butter with an electric mixer on medium speed until light and fluffy, about 2 minutes.
Step 9: Add powdered sugar. With the mixer on low, gradually add the sifted powdered sugar about 1 cup at a time, beating well after each addition. Scrape down the sides of the bowl as needed.
Step 10: Add Bailey's and flavorings. Add the Bailey's Irish Cream (start with 2 tablespoons for subtle or 3 tablespoons for stronger), vanilla extract, and salt. Beat on medium-high for 2-3 minutes until light and fluffy. If the frosting is too thick, add heavy cream 1 tablespoon at a time until you reach your desired spreading consistency.
Frost and Garnish
Step 11: Frost the brownies. Spread the frosting evenly over the completely cooled brownies using an offset spatula. For a rustic look, create swirls with the back of a spoon-I love this look for a more casual St. Patrick's Day party!
Step 12: Add garnishes. Top with chocolate shavings, a light dusting of cocoa powder, gold sprinkles, or green sanding sugar for a festive St. Patrick's Day touch. Get creative and have fun with it!
Step 13: Slice and serve. Use the parchment overhang to lift the brownies from the pan, then slice into 16 squares with a sharp knife. For the cleanest edges, chill the frosted brownies for 30 minutes first, and wipe the blade between each cut.
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Tips for Perfect Guinness Brownies
Don't overbake: This is the number one rule for fudgy brownies! The top should look set and slightly crackled, and a toothpick should come out with moist crumbs-not wet batter, but not completely clean either. When in doubt, pull them earlier. They'll continue to firm up as they cool.
Cool completely before frosting: I cannot stress this enough! If you frost warm brownies, the frosting will melt and slide right off. Give them a full hour at room temperature, or speed things up with 30 minutes in the fridge.
Sift your powdered sugar: This takes 30 seconds and makes a huge difference. Unsifted powdered sugar creates lumpy frosting-nobody wants that!
Room temperature ingredients matter: Room temperature eggs and softened butter mix more smoothly and create better texture in both the brownies and the frosting.
What if I don't have Guinness? Any dark stout will work beautifully. In a pinch, you can substitute ¾ cup strong brewed coffee for a similar depth of flavor without the stout.
Making a non-alcoholic version: Replace the Bailey's in the frosting with 3 tablespoons of Irish cream-flavored coffee creamer, or use 2 tablespoons heavy cream plus 1 teaspoon vanilla extract and ¼ teaspoon instant espresso powder.
Different pan sizes: I tested all three sizes and the 9x9 was the best fit, but other sizes work too! For a 9x13 pan, bake for 25-30 minutes for thinner brownies. For an 8x8 pan, bake for 40-45 minutes for extra thick, fudgy brownies.
Get clean cuts: Chill the frosted brownies in the refrigerator for 30 minutes before cutting. Use a sharp knife and wipe the blade clean between each cut. For the cleanest edges, run the knife under hot water and dry it before each slice.
Storage & Make-Ahead Tips
Room temperature (unfrosted): Store unfrosted brownies covered at room temperature for up to 3 days.
Refrigerator (frosted): Frosted brownies keep in an airtight container in the refrigerator for up to 5 days. Bring to room temperature for 15-20 minutes before serving for the best texture.
Freezer: Freeze unfrosted brownies for up to 3 months in a freezer-safe container with parchment between layers. Thaw completely before frosting.
Make-ahead strategy: Bake the brownies 1-2 days ahead and store covered at room temperature. Make the frosting and frost the brownies the day before or the day of your celebration for the freshest look.
Serving Suggestions
These Guinness Brownies with Irish Cream Frosting are perfect for:
- St. Patrick's Day parties
- Adult dessert platters
- Irish-themed dinner parties
- Potlucks and office celebrations
- After-dinner treats with coffee or Irish cream on the rocks
- Bake sales and fundraisers (label that they contain alcohol!)
- Game day watch parties
Package them in clear cellophane bags tied with green and gold ribbon for festive St. Patrick's Day gifts, or arrange them on a platter alongside Irish soda bread, mint chocolate cookies, and gold-wrapped chocolates for a stunning St. Patrick's Day dessert spread.
These Guinness Brownies with Irish Cream Frosting combine my love of simple, indulgent recipes with festive fun. The incredibly fudgy texture and that silky, slightly boozy frosting make them absolutely irresistible-and I promise, even your friends who say they don't like beer will be reaching for seconds!
From my family to yours, Happy St. Patrick's Day! ☘️
Pin this recipe for later and share your Guinness Brownies on Instagram-tag @marathonsandmotivation so I can see your beautiful creations!
Guinness Brownies with Irish Cream Frosting
Equipment
- 9x9-inch baking pan
Ingredients
Wet Ingredients (Brownies):
- 1 cup (2 sticks) unsalted butter cut into pieces
- 1¼ cups granulated sugar
- ¾ cup Guinness stout or other dark stout
- 2 teaspoons pure vanilla extract
- 2 large eggs room temperature
Dry Ingredients (Brownies):
- ¾ cup unsweetened Dutch-process cocoa powder
- 1 cup all-purpose flour
- ¼ teaspoon fine sea salt
Mix-ins (Optional):
Irish Cream Frosting:
- ½ cup (1 stick) unsalted butter softened to room temperature
- 3 cups powdered sugar sifted
- 2-3 tablespoons Bailey's Irish Cream adjust to taste; 3 tablespoons gives a stronger flavor
- 1 teaspoon pure vanilla extract
- Pinch fine sea salt
- 1-2 tablespoons heavy cream if needed
For Garnish (Optional):
- Chocolate shavings or cocoa powder for dusting
- Gold sprinkles or sanding sugar
- St. Patrick's Day themed sprinkles
Instructions
- Preheat and prepare: Position oven rack in the center of the oven and preheat to 350°F. Line a 9x9-inch baking pan with parchment paper, leaving overhang on two sides for easy removal. Lightly grease the parchment.
- Melt butter and add sugar and cocoa: In a medium saucepan, melt the butter over medium heat. Remove from heat and whisk in the sugar until combined. Add the cocoa powder and whisk until smooth and glossy.
- Add Guinness (or other Stout beer): Pour in the Guinness and whisk until combined—it will foam up slightly, which is normal.
- Add eggs and vanilla: Let the mixture cool for 5 minutes (you don't want to scramble the eggs). Whisk in the vanilla, then add the eggs one at a time, whisking well after each addition until the batter is smooth.
- Add dry ingredients: Add the flour and salt directly to the saucepan. Using a spatula or wooden spoon, stir until just combined—do not overmix. Fold in the chocolate chips if using.
- Bake: Pour the batter into the prepared pan and spread evenly. Bake for 35-40 minutes, until the top is set and a toothpick inserted in the center comes out with moist crumbs (not wet batter). For fudgier brownies, pull them at 35 minutes. The brownies will continue to set as they cool.
- Cool completely: Let the brownies cool in the pan on a wire rack for at least 1 hour before frosting. For cleaner cuts, refrigerate for 30 minutes after cooling.
- Make the frosting: In a large bowl, beat the softened butter with an electric mixer on medium speed until light and fluffy, about 2 minutes. With the mixer on low, gradually add the sifted powdered sugar, about 1 cup at a time, beating well after each addition.
- Add Bailey's and flavorings: Add the Bailey's (start with 2 tablespoons for a subtle flavor or use 3 tablespoons for a stronger taste), vanilla, and salt. Beat on medium-high for 2-3 minutes until light and fluffy. If the frosting is too thick, add heavy cream 1 tablespoon at a time until you reach your desired consistency.
- Frost and garnish: Spread the frosting evenly over the cooled brownies using an offset spatula. For a rustic look, create swirls with the back of a spoon. Top with chocolate shavings, a light dusting of cocoa powder, gold sprinkles or green sanding sugar for a festive touch.
- Slice: Use the parchment overhang to lift the brownies from the pan, then slice into squares with a sharp knife.
- STORAGE:
- Store unfrosted brownies covered at room temperature for up to 3 days or frozen for up to 3 months. Frosted brownies keep in an airtight container in the refrigerator for up to 5 days. Bring to room temperature for 15-20 minutes before serving.
Notes
Will these brownies taste like beer: Not at all! The baking process transforms the stout—you won't taste beer, but you'll notice the brownies are extra moist with a deeper, more complex chocolate flavor. Even people who don't like beer love these brownies.
What if I don't have Guinness: Any dark stout will work well. In a pinch, you can substitute ¾ cup strong brewed coffee for a similar depth of flavor without the stout.
How do I know when the brownies are done: The top should look set and slightly crackled, and a toothpick inserted in the center should come out with moist crumbs—not wet batter, but not completely clean either. When in doubt, pull them earlier.
Can I make a non-alcoholic version of the frosting: Yes! Replace the Bailey's with 3 tablespoons of Irish cream-flavored coffee creamer, or use 2 tablespoons heavy cream plus 1 teaspoon vanilla extract and ¼ teaspoon instant espresso powder.
How do I get clean brownie cuts: Chill the frosted brownies in the refrigerator for 30 minutes before cutting. Use a sharp knife and wipe the blade clean between each cut. For the cleanest edges, run the knife under hot water and dry it before each slice.
Can I use a different pan size: Yes! I tested all three sizes and the 9x9 was the best fit, but other sizes work too. For a 9x13 pan, bake for 25-30 minutes for thinner brownies. For an 8x8 pan, bake for 40-45 minutes for extra thick, fudgy brownies.
Nutrition
