1. Preheat your oven to 350°F (175°C). Grease a 9×13 inch baking dish and set aside.
2. In a skillet over medium heat, cook the sausage until browned and cooked through. Drain the excess fat.
3. In a large mixing bowl, whisk together the eggs, milk, salt, pepper, and dried mustard until well combined.
4. Layer the cubed bread on the bottom of the prepared baking dish. Top with the cooked sausage, then sprinkle with cheddar cheese and diced bell peppers if using.
5. Pour the egg mixture evenly over the layers in the baking dish. Press down gently to ensure all the bread is soaked.
6. Bake in the preheated oven for about 40-45 minutes, or until the casserole is set and the top is golden brown. Let it cool for a few minutes before serving.

As the casserole bakes, the house fills with the rich, inviting aroma that takes me back to those cherished mornings with Mama Lou and Ouma, chatting and laughing as we set the table together.