You can make a frittata with a huge variety of ingredients. I happened to have fairly standard ingredients on hand from making a boatload of French omelettes last week, so I went with that. Recipe and tips from epicurious and bonappetit.

Other ingredients to consider: potatoes, sausages, ham, roasted red bell peppers, tomatoes, zucchini, crumbled bacon, and herbs like parsley, dill, basil. 

Breakfast Frittata

• In an 10-inch cast-iron skillet, saute 1 onion diced in oil for a few minutes.
• Add 8 oz crimini mushrooms sliced. Saute, trying to evaporate all liquid.
• Whisk 10-12 eggs, 1/2 cup milk, 1/2 cup shredded cheese (fontina, gruyere, cheddar, pecorino romano), 1 tsp kosher salt, generous pepper.
• Spread handful (~1 oz) quickly blanched then wrung dry baby spinach.
• Pour in egg mixture. Use chopsticks to lift up filling a little. Cook without stirring 5 minutes, until edges start to set. Sprinkle top with 1/4 cup cheese.
• Bake at 350 F for 22-27 minutes, until golden brown and set. Don’t overbake.