Step 1: Prepare Your Vegetables (If Necessary)

• Roast Vegetables (Optional): If using roasted vegetables, preheat your oven to 400°F (200°C). Toss your chosen vegetables (bell peppers, onions, zucchini, etc.) with olive oil, salt, and pepper. Roast for 20-30 minutes, or until tender and slightly caramelized. Let cool slightly before adding to the frittata.
• Sauté Vegetables (Optional): If using sautéed vegetables, heat a tablespoon of olive oil in a skillet over medium heat. Add your chosen vegetables (mushrooms, spinach, onions, etc.) and sauté until tender-crisp and wilted (for spinach). Season with salt and pepper. Set aside to cool slightly.
• Prepare Other Vegetables: If using sun-dried tomatoes, artichoke hearts, olives, or roasted red peppers, drain them well and chop them into smaller pieces if necessary.

Step 2: Preheat Oven (If Baking)

• Preheat Oven (For Oven-Baked or Stovetop-Oven Finish): Preheat your oven to 375°F (190°C).

Step 3: Prepare the Egg Mixture

• Whisk Eggs: In a large bowl, whisk together the eggs, milk or cream (or dairy-free alternative), grated Parmesan cheese (or vegetarian alternative), salt, and black pepper until well combined and slightly frothy. Don’t over-whisk; just ensure everything is incorporated.

Step 4: Assemble and Cook the Frittata (Choose Your Cooking Method)

Method 1: Stovetop with Oven Finish (Recommended for Even Cooking and Easy Release)

• Heat Skillet: Choose an oven-safe skillet (cast iron, stainless steel with oven-safe handle, or ceramic oven-safe skillet) that is approximately 8-10 inches in diameter. Heat a tablespoon of olive oil or butter in the skillet over medium heat.
• Add Vegetables: If you haven’t already sautéed your vegetables, you can sauté them directly in the skillet now. Otherwise, if using pre-cooked vegetables, simply distribute them evenly over the bottom of the skillet.
• Pour Egg Mixture: Pour the egg mixture evenly over the vegetables in the skillet.
• Cook on Stovetop: Cook on the stovetop over medium-low heat for 8-10 minutes, or until the edges of the frittata are set and the center is still slightly jiggly but mostly cooked. You can gently lift the edges of the frittata with a spatula to allow the uncooked egg mixture to flow underneath.
• Add Cheese (Optional): If using additional cheese (beyond the Parmesan in the egg mixture), sprinkle it evenly over the top of the frittata now.
• Bake in Oven: Transfer the skillet to the preheated oven and bake for 10-15 minutes, or until the frittata is set in the center and lightly golden brown on top. A toothpick inserted into the center should come out mostly clean.
• Cool Slightly: Remove the frittata from the oven and let it cool in the skillet for a few minutes before slicing and serving. This allows it to set further and makes it easier to cut.

Method 2: Oven-Baked Frittata (Simpler, Entirely Oven-Based Cooking)

• Grease Baking Dish: Lightly grease an 8-inch square baking dish or a 9-inch pie dish with olive oil or butter.
• Arrange Vegetables: Spread your chosen vegetables evenly over the bottom of the greased baking dish.
• Pour Egg Mixture: Pour the egg mixture evenly over the vegetables in the baking dish.
• Add Cheese (Optional): If using cheese beyond the Parmesan in the egg mixture, sprinkle it evenly over the top.
• Bake in Oven: Bake in the preheated oven for 25-35 minutes, or until the frittata is set in the center and lightly golden brown on top. A toothpick inserted into the center should come out mostly clean.
• Cool Slightly: Remove the frittata from the oven and let it cool slightly in the baking dish for a few minutes before slicing and serving.

Step 5: Serve and Enjoy!

• Slice the frittata into wedges and serve warm, at room temperature, or even chilled. Garnish with fresh herbs, extra Parmesan cheese, or a dollop of yogurt or sour cream (optional).