Start by preparing an 11 x 7 baking dish with cooking spray or butter.
Toast the English muffins and break them into chunks.
Then combine the English muffins, chopped red and green bell pepper, diced onion and sliced shiitake mushrooms in a baking dish.
Next, add the cheese and diced Hatfield ham, toss with a spoon to combine.
In a medium bowl, blend together eggs, milk, Dijon mustard, garlic powder, Worcestershire sauce and pepper with a hand mixer.
Pour egg mixture over the muffin mixture. Cover and place in the refrigerator for at least 2 hours or overnight. The longer the dish sits, the more the consistency of the strata will be like a custard.
When ready to bake, remove dish from refrigerator and preheat oven to 350 degrees. Then, bake for approximately 35 to 40 minutes, or until eggs set and the top lightly browns. If desired, take out of oven after 30 minutes and sprinkle with cheese, then finish off in the oven.
After removing from oven, let stand for 10 minutes before serving. Then, enjoy hot!