📖 Instructions

1. **Preheat Your Oven:** About an hour before you plan to serve the casserole, preheat your oven to 375°F (190°C). This gives it plenty of time to come to temperature.
2. **Prepare Your Baking Dish:** Lightly grease a 9x13 inch baking dish with cooking spray or butter. This step is super important to prevent sticking and make cleanup easier.
3. **Cube the Bread:** Take your loaf of day-old bread and cut it into 1-inch cubes. You want about 6 cups worth. Stale bread works best here as it absorbs the egg mixture without getting too soggy. Distribute these cubes evenly over the bottom of your prepared baking dish.
4. **Cook the Sausage:** In a large skillet, cook the breakfast sausage over medium-high heat, breaking it up with a spoon as it browns. Once it’s fully cooked and no longer pink, drain off any excess grease. This is important to avoid a greasy casserole. Scatter the cooked sausage evenly over the bread cubes in the baking dish.
5. **Add the Cheese:** Sprinkle 2 cups of shredded cheddar cheese over the sausage and bread layer. Don't be shy; cheese is key to that gooey, delicious texture!
6. **Whisk the Egg Mixture:** In a large bowl, crack 8 large eggs. Add 2 cups of milk, 1 teaspoon of Dijon mustard (it adds a subtle tang that really brightens the flavor!), and a generous pinch of salt and black pepper. Whisk everything together thoroughly until the eggs are well-beaten and combined with the milk, looking smooth and slightly frothy.
7. **Pour and Cover:** Carefully pour the egg mixture evenly over the bread, sausage, and cheese in the baking dish. Make sure all the bread cubes are well-coated and soaking in the liquid. If some pieces are still dry, gently press them down with the back of a spoon.
8. **Refrigerate Overnight:** Cover the baking dish tightly with plastic wrap or aluminum foil. Place it in the refrigerator for at least 8 hours, or preferably overnight (up to 24 hours). This allows the bread to fully absorb the egg mixture and flavors to meld beautifully.
9. **Bake the Casserole:** The next morning, remove the casserole from the refrigerator about 30 minutes before baking to let it come closer to room temperature. Take off the plastic wrap or foil. Bake for 45-55 minutes, or until the casserole is golden brown on top, puffed up, and a knife inserted into the center comes out clean. If you see it browning too quickly, you can loosely tent it with foil.
10. **Rest and Serve:** Once baked, remove the casserole from the oven and let it rest for 5-10 minutes before serving. This resting period allows the casserole to set, making it easier to cut into neat squares. Garnish with fresh chopped parsley or chives if you like. Enjoy your effortless, delicious breakfast!