Preheat oven to 350ºF. Grease a 13x9-inch baking dish with butter or nonstick cooking spray.
Cook and crumble breakfast sausage in a large skillet over medium-high heat. Leaving the drippings in the pan, transfer the sausage to a paper towel lined plate.
If your meat didn’t produce ¼ cup drippings, add oil or butter to that amount. Whisk flour into the grease, and allow it to cook for 2-3 minutes.
Add 1 cup of the milk to the mixture and whisk quickly. This initial mixture will thicken and cook quickly.
Once well combined, add an additional cup of milk and stir until well combined. Allow the mixture to come to a light simmer then turn heat to medium-low.
As the mixture thickens, add ½ cup milk and seasoning salt or salt and black pepper to taste. Simmer 3-5 minutes.
Cut each biscuit into 6 pieces. Spread in an even layer in the prepared baking dish.
Set aside ½ cup of the cooked sausage. Sprinkle the remaining sausage and shredded cheese over the biscuit pieces evenly.
In a large bowl, whisk together eggs, the remaining cup of milk, and seasoning salt or salt and black pepper. Pour evenly into the baking dish.
Pour the gravy evenly on top, then sprinkle with the remaining cooked sausage
Bake for 35-45 minutes, or until eggs and biscuits are cooked through.