01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish with butter or nonstick cooking spray.
02 - In a large skillet over medium heat, brown the sausage, breaking it apart with a spoon until fully cooked. Drain excess fat.
03 - Arrange half of the English muffin cubes in the baking dish. Top with half of the cooked sausage, half the red bell pepper, half the green onion, and half the cheddar cheese. Repeat with remaining cubes, sausage, vegetables, and cheese.
04 - In a mixing bowl, whisk together eggs, whole milk, heavy cream, garlic powder, salt, black pepper, and melted butter until smooth.
05 - Evenly pour egg mixture over layered ingredients, pressing down gently with a spatula so bread absorbs custard.
06 - Cover assembled dish with foil and refrigerate for at least 30 minutes or overnight for optimal texture.
07 - Bake, covered, for 30 minutes at 350°F.
08 - Remove foil and bake for an additional 15 minutes, or until top is golden and center is set.
09 - Allow casserole to rest for 10 minutes. Slice and serve warm.