12 large eggs
2 cups fresh ricotta (I like sheep's-milk ricotta)
Salt and pepper
4 tablespoons olive oil
4 cloves garlic, chopped
1 16-ounce bag frozen chopped spinach, thawed and squeezed dry in a kitchen towel
1 cup shredded provolone
1 cup shredded low-moisture mozzarella
16 thin slices good-quality pepperoni
About 1/2 teaspoon dried oregano
A few leaves of basil, torn if large
Position a rack in the center of the oven and preheat to 450°F.
In a medium bowl, whisk the eggs and ricotta; season with salt and pepper.
Preheat a 10-inch cast-iron skillet over medium-high. Add the oil, four turns of the pan, and swirl to coat the bottom and the sides of the pan. Add the garlic; cook until aromatic, stirring constantly, about 30 seconds. Add the spinach, loosening it up with your fingers as you add it to the pan; season with salt and pepper. Pour in the egg mixture and stir to mix in the spinach. Cook until the sides begin to set a bit, about 2 minutes, running a heatproof spatula around the edges of the skillet to loosen the frittata from the pan; transfer to the oven.
Bake until set around the edges but still slightly loose in the center, 10-12 minutes. Top with the provolone, mozzarella, pepperoni and oregano then return to the oven. Bake until bubbly and browned in spots, 5-6 minutes more. Top with the basil and serve.