1-Preparing the Egg Mixture: Start by cracking 12 large eggs into a large mixing bowl. Add 1/2 cup of heavy cream, 1/2 teaspoon of kosher salt, and 1/2 teaspoon of black pepper. Whisk the mixture thoroughly until well combined and slightly frothy. This step is crucial for incorporating air into the eggs, which helps ensure even cooking and a fluffy texture. Incorporate air vigorously into the mixture to maximize fluffiness.

Next, add the cheese blend to the egg mixture. This includes 1/2 cup shredded Gruyere, 1/2 cup shredded fontina, 1/2 cup crumbled feta, and 1/4 cup grated Parmesan. Gently stir to combine, being careful not to overmix which could deflate the eggs you’ve just aerated.

2-Cooking the Vegetables: Heat 2 tablespoons of olive oil in a 10-inch cast iron skillet over medium heat. Using a cast iron skillet is ideal as it provides even heat distribution and can safely transfer from stovetop to oven. Once the oil is hot, add 2 cups of halved cherry or grape tomatoes, 1 cup of thinly sliced fresh basil, 1 teaspoon of red pepper flakes, and 1 teaspoon of dried Italian seasoning. Cook this mixture for 4 to 5 minutes, allowing the tomatoes to soften and release their juices while the basil becomes fragrant.

Add 1/3 cup of minced scallions and 2 tablespoons of minced shallots, cooking for 2 more minutes until softened. Then, add 1 1/2 teaspoons of minced garlic and cook until fragrant, about 1 minute. Finally, toss in 4 cups of fresh baby spinach, sautéing for 1 to 2 minutes until wilted. Season with additional salt and pepper to taste before reducing heat to medium-low.

3-Combining and Cooking: Pour the egg and cheese mixture over the sautéed vegetables in the skillet. Gently stir to combine, ensuring the vegetables are evenly distributed throughout the eggs. Cook on the stove until the eggs begin to set around the edges, about 3 to 5 minutes. You should see the bottom and edges firming up while the center remains slightly liquid.

Transfer the skillet to a preheated 350°F oven. Bake for 15 to 20 minutes until the center is set and the top is golden brown. The frittata should have a slight jiggle in the very center when gently shaken, but not appear liquid.

4-Resting and Serving: Remove the frittata from the oven and allow it to rest for 5 minutes in the skillet. This resting period is essential as it helps the frittata maintain its structure for easier handling and presentation. After resting, carefully run a spatula around the edges to loosen from the pan. Invert the frittata onto a serving plate or cut directly from the skillet. This delicious dish pairs perfectly with party tartines for brunch or can stand alone as a satisfying main course.