Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
In a large skillet, cook Italian sausage over medium-high heat, crumbling it as it cooks. When sausage is almost cooked through, add onion, bell pepper, garlic, oregano, basil, red pepper flakes, salt, and pepper. Cook for 5 minutes, stirring occasionally. Remove from heat and set aside.
In a medium saucepan, melt butter over medium heat. Stir in flour and cook for 1 minute. Gradually whisk in milk and bring to a boil. Cook, stirring constantly, until mixture thickens. Remove from heat and set aside.
In the prepared baking dish, layer the bottom with cubed French bread. Sprinkle with Parmesan cheese, then top with cooked sausage mixture. Pour the milk mixture over the sausage layer, and top with mozzarella cheese. In a large bowl, whisk together eggs, parsley, salt, and pepper. Pour egg mixture over the cheese layer.
Bake in preheated oven for 45 minutes, or until eggs are set. Let cool for 5 minutes before serving.
Interesting Facts
Strata is a classic breakfast casserole that is relatively easy to make and great for feeding a crowd.
This dish can also be made ahead of time and refrigerated overnight before baking.
It is also customizable - you can switch up the ingredients to suit your taste.