Preheat your oven to 350 degrees Fahrenheit. Spray a 9 by 13 inch baking dish with cooking spray and set aside. Heat a heavy-bottomed skillet over medium heat. Cook the bacon and the sausage together, breaking up the sausage. Stir frequently until both the bacon and the sausage are completely cooked through, about 12 to 15 minutes. Remove from the skillet with a slotted spoon and drain on a towel.
1/2 pound breakfast sausage, 6 slices thick cut bacon
While the sausage and bacon are cooking, start making the eggs by preheating a large skillet over medium-low heat.
In a large bowl whisk together the eggs, milk, kosher salt, and pepper.
12 large eggs, 2 tablespoons milk, 1/4 teaspoon black pepper, 1/2 teaspoon kosher salt
Melt the butter in the preheated skillet. Pour in the egg mixture. Allow it to set for a moment, about 30 seconds, and then using a spatula, start pulling the edge of the mixture toward the center of the pan. Continue to do this as the eggs begin to solidify. Once the eggs are light and fluffy (about 7 to 10 minutes), remove them from the heat.
2 tablespoons butter
Slice your slider rolls in half so that you have a bottom layer and a top layer. Place the bottom layer in the prepared casserole dish. (The tops might not all stay together, and that is okay. You will be able to arrange them at the end.)
12 slider rolls
Melt the butter. Whisk in the garlic salt and the ground mustard. Divide the butter mixture in two. Brush the bottom half of the rolls with half the mixture.
8 tablespoons unsalted butter, 1 teaspoon garlic salt, 1 teaspoon ground mustard
Add the egg layer. Then add the bacon and sausage layer. Finally, add the cheese. Add the tops of the rolls on top of the cheese.
Brush the tops of the rolls with the remaining butter mixture. Cover the casserole dish with foil and bake for 20 minutes. Remove the foil and bake for 5 more minutes.