📖 Instructions

1. **Preheat Your Oven:** Before you do anything else, preheat your oven to 375°F (190°C). This ensures it's perfectly hot when your casserole is ready to bake, leading to even cooking and a beautiful golden-brown top.
2. **Prepare the Sausage:** In a large skillet, cook your breakfast sausage over medium-high heat. Break it up with a spatula as it cooks until it's nicely browned and completely cooked through. This usually takes about 5-7 minutes. Once cooked, drain any excess grease thoroughly; nobody wants a greasy casserole! Set the cooked sausage aside in a bowl.
3. **Sauté the Aromatics (Optional but Recommended):** In the same skillet (or a clean one if you prefer), add a tiny bit of olive oil if needed. Sauté your chopped onion and bell pepper (if using) for 5-7 minutes until they soften and the onion becomes translucent. This step adds a lovely depth of flavor. Add these to the bowl with the sausage.
4. **Dice the Bread:** While the sausage is cooking, cut your day-old bread into 1-inch cubes. Stale bread works best here as it absorbs the egg mixture without getting too soggy. Evenly distribute these bread cubes into a lightly greased 9x13 inch baking dish.
5. **Layer the Good Stuff:** Sprinkle the cooked sausage and sautéed veggies (if used) evenly over the bread cubes in the baking dish. Then, generously sprinkle about half of your shredded cheese over the sausage and bread. This creates delicious layers of flavor.
6. **Whisk the Egg Mixture:** In a large mixing bowl, whisk together the eggs, milk, Dijon mustard, salt, black pepper, garlic powder, and onion powder until everything is well combined and slightly frothy. The Dijon mustard might seem odd, but trust me, it adds a subtle tang that really elevates the flavor profile without making it taste like mustard.
7. **Pour and Soak:** Carefully pour the egg mixture evenly over the bread, sausage, and cheese in the baking dish. Make sure all the bread cubes get a good soak! Gently press down on the bread with the back of a spoon or spatula to help it absorb the liquid. This is key for a consistently moist casserole.
8. **The Waiting Game (Chill Time):** Cover the baking dish tightly with plastic wrap and refrigerate for at least 30 minutes. For the best flavor and texture, I highly recommend making it the night before and letting it chill in the fridge overnight (8-12 hours). This allows the bread to fully absorb the egg mixture and all the flavors to meld beautifully.
9. **Final Cheese Layer & Bake:** Remove the casserole from the refrigerator and let it sit at room temperature for about 15-20 minutes while your oven finishes preheating. Uncover it and sprinkle the remaining half of the shredded cheese over the top. Pop the dish into your preheated oven.
10. **Bake Until Golden:** Bake for 45-55 minutes, or until the casserole is puffed up, golden brown on top, and a knife inserted into the center comes out clean. If you see it browning too quickly, you can loosely tent it with aluminum foil. The internal temperature should reach 160°F (71°C).
11. **Rest and Serve:** Once baked, remove the casserole from the oven and let it rest for 5-10 minutes before slicing and serving. This resting period helps the casserole set, making it easier to cut and preventing it from falling apart. Serve warm and enjoy your delicious morning hug!