1. 1. Prepare the Baking Dish: Lightly grease a 9×13-inch baking dish with the tablespoon of unsalted butter. This prevents sticking and ensures easy cleanup.

2. 2. Arrange the Sourdough: Spread the cubed sourdough bread evenly in the prepared baking dish. If you’re adding cooked sausage or bacon, sprinkle it over the bread cubes at this stage.

3. 3. Saute the Vegetables: In a small skillet, saute the chopped bell peppers and onion over medium heat until softened, about 5-7 minutes. Scatter the sauteed vegetables over the bread cubes.

4. 4. Whisk the Egg Mixture: In a large bowl, whisk together the eggs, milk, heavy cream (if using), salt, and black pepper until well combined and slightly frothy. Stir in 1 cup of shredded cheddar cheese.

5. 5. Assemble and Soak: Pour the egg mixture evenly over the bread and vegetable mixture in the baking dish. Gently press down on the bread cubes with a spatula to ensure they are fully submerged and soaking up the liquid.

6. 6. Chill Overnight: Cover the baking dish tightly with plastic wrap and refrigerate for at least 8 hours, or preferably overnight. This allows the bread to fully absorb the egg mixture, creating that wonderful custardy texture.

7. 7. Bake in the Morning: The next morning, preheat your oven to 375 F (190 C). Remove the breakfast bake from the refrigerator and let it sit on the counter for about 20-30 minutes while the oven preheats. This helps it bake more evenly.

8. 8. Finish and Serve: Uncover the dish, sprinkle with additional shredded cheese if desired, and bake for 45-55 minutes, or until the top is golden brown and the center is set. A knife inserted into the center should come out clean. Let it rest for 5-10 minutes before slicing and serving.