Place a large (10 inch wide) nonstick skillet that is oven safe on the stovetop. Heat over medium heat.
While the skillet is heating, prepare your ingredients by halving the tomatoes and cutting the mozzarella into chunks approximately 1/4-1/3 inches. Chop the basil.
In a small bowl, whisk together the eggs, Parmesan cheese, halved cherry tomatoes, mozzarella cheese chunks, fresh basil, salt, and black pepper.
Add the oil to the skillet. When warm, add the egg mixture. Stir briefly. Let the egg mixture cook until the edges begin to set, approximately 3-5 minutes.
Turn off the stove and place the oven safe skillet in the oven. Bake until the eggs are completely cooked through and the frittata is dry to the touch on top, approximately 10-12 minutes.
Remove the frittata from the oven. Run a rubber spatula around the edge of the frittata to loosen it and either slide it out or flip it onto a plate. Serve immediately and top with additional fresh basil if desired.
To ensure a completely vegetarian dish, make sure to use vegetarian cheese.A non-stick skillet is best, but you can also use a cast iron skillet. The egg tends to stick more in cast iron, making it difficult to flip out if you choose to do so.The smaller the skillet, the thicker your frittata will be and the longer it will need to cook. The larger the skillet, the thinner the frittata and the faster it cooks. I use a 10 inch skillet for this recipe.You can substitute 1 teaspoon of dried basil for the fresh, however fresh basil is recommended for optimal flavor.