01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish.
02 - In a large skillet over medium heat, crumble and cook the sausage until browned. Transfer to a plate, draining excess fat.
03 - In the same skillet, sauté the chopped onion and diced red bell pepper until softened.
04 - In a large bowl, whisk together eggs, milk, salt, black pepper, dried mustard, and paprika until well combined.
05 - Spread the cubed bread evenly in the prepared baking dish. Top with cooked sausage, sautéed vegetables, and 1½ cups of the cheddar cheese.
06 - Pour the egg mixture evenly over the layers and gently press down to ensure the bread is soaked.
07 - Sprinkle the remaining 1/2 cup cheddar cheese on top.
08 - Bake uncovered for 40–45 minutes, until the casserole is set and golden brown.
09 - Let cool for 5–10 minutes before slicing. Garnish with chopped chives or parsley, if desired. Serve warm.