Creating a frittata is simple when you follow these steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C).
2. Prepare the Egg Mixture: In a large bowl, whisk together the eggs, milk, salt, and pepper until well combined.
3. Sauté Vegetables: In an oven-safe skillet, heat olive oil or butter over medium heat. Add the diced vegetables and sauté until softened, about 5 minutes.
4. Add Meat: If using, add the cooked meat to the skillet and stir until heated through.
5. Combine Ingredients: Pour the egg mixture over the sautéed vegetables and meat, ensuring even distribution.
6. Sprinkle Cheese: Sprinkle shredded cheese evenly over the top.
7. Cook on the Stovetop: Cook on the stovetop for about 5-7 minutes, or until the edges start to set.
8. Transfer to Oven: Carefully transfer the skillet to the preheated oven and bake for 15-20 minutes, or until the frittata is set and lightly golden.
9. Cool and Slice: Remove from the oven and let cool for a few minutes. Slice into wedges for serving.
10. Garnish: Top with fresh herbs, if desired, before serving.

These straightforward steps will guide you in creating an incredible frittata that is sure to impress.