Grease a 13x9-inch baking dish and set aside.
In a large bowl, whisk together the eggs, milk, mustard, paprika, garlic powder, salt, and pepper until well blended.
Place half of the English muffin pieces in the bottom of the prepared baking dish.
Sprinkle half of the chopped, cooked back bacon over the top of the English muffins.
Repeat the English muffin and bacon layers once more.
Pour the egg mixture over the top of the bacon and English muffins.
Allow the dish to sit in the refrigerator for at least 1 hour before baking.
When ready to bake, preheat the oven to 350°F and bake for 50 minutes or until a toothpick comes out clean when inserted into the center of the casserole.