Step 1: Prepare Your Oven and Vegetables (Preheating and Prepping)

• Preheat your oven to 375°F (190°C): It’s crucial to preheat your oven properly to ensure even cooking and a beautifully set frittata. While the oven preheats, you can focus on preparing the vegetables.
• Prepare the Vegetables: Wash and chop all your chosen vegetables into bite-sized pieces. Dicing onions, bell peppers, zucchini, and squash into roughly ½-inch pieces ensures they cook evenly. Slice mushrooms and halve or quarter cherry tomatoes. Roughly chop spinach or kale. Mince the garlic. Having all your vegetables prepped and ready to go will streamline the cooking process.

Step 2: Sauté the Vegetables (Building Flavor)

• Heat Olive Oil in the Skillet: Place your oven-safe skillet over medium heat. Add 2 tablespoons of olive oil and let it heat up until it shimmers slightly. This indicates the oil is hot enough to start sautéing.
• Sauté Onions and Garlic: Add the diced onions to the skillet and sauté for 3-5 minutes, until they become softened and translucent. Stir occasionally to prevent sticking and ensure even cooking. Once the onions are softened, add the minced garlic and sauté for another minute until fragrant. Be careful not to burn the garlic, as it can become bitter.
• Add Heartier Vegetables: Add any heartier vegetables that require more cooking time, such as bell peppers, broccoli florets, zucchini, or squash. Sauté these for 5-7 minutes, stirring occasionally, until they start to soften slightly.
• Add Mushrooms and Greens (If Using): If using mushrooms, add them to the skillet and sauté until they release their moisture and begin to brown slightly. If using spinach or kale, add them in batches and sauté until they wilt down. Spinach wilts very quickly, while kale may take a bit longer.
• Season the Vegetables: Season the sautéed vegetables with salt, freshly ground black pepper, and red pepper flakes (if using). Taste and adjust seasoning as needed. Seasoning at this stage is crucial for building layers of flavor in your frittata.
• Remove from Heat: Once the vegetables are tender-crisp and nicely sautéed, remove the skillet from the heat.

Step 3: Whisk the Egg Mixture (Creating the Base)

• Whisk Eggs, Milk/Cream, and Cheese: In a large bowl, crack the 8 large eggs. Add ½ cup of milk or cream and ½ cup of grated cheese (or cheese blend). Whisk vigorously until the eggs, milk/cream, and cheese are thoroughly combined and slightly frothy. Whisking incorporates air, which will help make the frittata light and fluffy.
• Season the Egg Mixture: Season the egg mixture with salt and freshly ground black pepper. Be mindful that some cheeses are already salty, so taste the mixture before adding too much salt. You can also add a pinch of dried herbs like Italian seasoning, thyme, or oregano to the egg mixture for extra flavor.

Step 4: Assemble and Bake the Frittata (Cooking to Perfection)

• Pour Egg Mixture over Vegetables: Pour the whisked egg mixture evenly over the sautéed vegetables in the skillet. Use a spatula to gently distribute the vegetables evenly within the egg mixture.
• Top with Remaining Cheese (Optional): If desired, sprinkle the remaining ½ cup of grated cheese over the top of the frittata. This will create a beautifully golden and cheesy crust.
• Bake in the Preheated Oven: Carefully transfer the skillet to the preheated oven and bake for 25-35 minutes, or until the frittata is set and lightly golden brown on top. The frittata is done when it is puffed up, no longer jiggly in the center, and a knife inserted into the center comes out clean. Baking time may vary slightly depending on your oven and the depth of your skillet.
• Broil for Extra Browning (Optional): If you want a more deeply golden and slightly crispy top, you can broil the frittata for the last 1-2 minutes of baking. Keep a close eye on it while broiling to prevent burning.

Step 5: Cool and Serve (Finishing Touches)

• Let it Cool Slightly: Remove the frittata from the oven and let it cool in the skillet for a few minutes before slicing. This allows the frittata to set further and makes it easier to slice and serve.
• Garnish (Optional): Garnish the frittata with fresh herbs like chopped parsley, chives, or basil before serving. This adds a pop of freshness and visual appeal.
• Slice and Serve: Slice the frittata into wedges and serve warm.