Preheat. Heat oven to 375F. Grease a 9x13-inch baking dish.
Add the crescent base. Unroll crescent dough and press into the bottom of the dish. Pinch seams together and press slightly up the sides.
Add fillings. Sprinkle cooked sausage (or other add-ins) evenly over the dough. Add 1 cup of the cheese.
Make the egg mixture. In a bowl, whisk eggs, milk, salt, pepper, and optional seasonings until smooth.
Assemble. Pour egg mixture evenly over the casserole. Top with remaining 1 cup cheese.
Bake. Bake 30 to 40 minutes, until the center is set and a knife inserted comes out mostly clean.
Rest and serve. Rest 10 minutes before slicing. Serve warm with salsa or hot sauce if you like.