You may prepare this egg casserole dish the night before—and just bake in the oven the next morning. Make it easy on yourself, especially if you have guests over!
Spray a 9x13-inch casserole pan with cooking spray. Saute meats and drain. Melt butter. Add garlic, mushrooms, and green onions, and saute then add to meat and mix thoroughly. Beat eggs with milk, mustard, and salt. Add toast and ¼ cup of cheese. Add meat and blend together. Fill pan with mixture and sprinkle with remaining cheese. Cover and refrigerate overnight. Preheat oven to 350 and bake 40-45 minutes.