Preheat oven to 375°F, with rack at center.
In a large mixing bowl, combine all the eggs. Season the eggs with loaded salt and pepper and all but1 tablespoon of the parsley and the red pepper flakes (if using) and whisk to combine. Whisk ricotta, then Parm and pecorino into the egg mixture.
A note about the cheeses: depending on what store you shop at cheese availability may be different. Many companies offer some of these cheeses in blends, don’t be afraid to experiment! I last used a romano, parm, asiago blend because that was the closest thing. Just as long as you are adding the correct amount of cheese (3 cups) and it has a similar taste profile it will be just fine, maybe even better!
Heat a 12-inch nonstick oven-safe skillet over medium heat with EVOO, melt butter into oil and swirl to melt. My personal favorite is my cast iron skillet but any oven safe variety will work. When butter foams, add the egg mixture and gently turn and settle the mixture until the bottom sets a bit.
Transfer to the oven and bake 15 to 17 minutes until set enough to add the remaining shredded cheeses to the top of the frittata. Bake 10 to 15 minutes more until very puffed and golden. Cool on wire rack to set, then slide onto serving platter or large plate.
Top the frittata with reserved parsley and more red pepper flakes (if using).
VARIATIONS: This is just a basic cheese frittata. You can add vegetables and meats to it. Just make sure the vegetables and meats are cooked so that they don’t add extra water and make your frittata soggy! Try my breakfast sausage seasoning if you want to add homemade sausage!https://rachelsspicecompany.com/product/breakfast-sausage-seasoning/