Healthy Meal Prep Breakfast Sandwiches

1. Mix together the eggs, garlic, red pepper flakes, salt, and pepper. 
2. Then add in milk, chopped spinach, chopped mushrooms, and feta cheese. 
3. Grease 2 donut pans or a casserole dish. If using a casserole dish, you will cut the cooked egg mixture into 12 pieces when done. Cooking times should be similar for both methods. 
4. Bake at 400F for 20 minutes. 
5. Once baked, assemble your sandwiches. 
6. Wrap in foil and freeze overnight, or for up to 3 months. 
7. To reheat, microwave with a small glass of water or warm in an air fryer/toaster oven.