In a large skillet, cook sausage over medium heat until no longer pink, breaking into crumbles; drain and transfer to a greased 9x13-inch baking dish.

In same skillet, heat butter over medium heat. Add the onion and mushrooms; sauté until tender (10-15 minutes). Stir in spinach. Spoon vegetable mixture over sausage.

In a bowl, whisk eggs and milk; pour mixture over meat & vegetables. Sprinkle with cheeses and paprika.

Bake uncovered at 350 degrees for 45-50 minutes or until the center is set. Let stand 10 minutes before serving.

NOTE: You can assemble cooked meat and vegetables the night before, cover dish and put in refrigerator. In the morning add eggs, cheeses and paprika then bake. Serves 12