Combined all 12 eggs, a large pinch of salt, pepper and cream in a large bowl. Whisk very well to combine! You can use a hand mixer on low if that’s easier. Egg mixture should be light yellow with no visible streaks of white.
Preheat your oven to 425 degrees.
Heat a large 12 inch cast iron or oven safe skillet over medium heat.
Once your pan is hot, add a tbsp of oil, diced onion, pinch of salt, and pepper. Sauté about 5 minutes until onions are soft and translucent, stirring occasionally.
Once onions are soft, remove them from the pan and set aside.
In the same pan, add in a tablespoon of oil and green beans with a pinch of salt and pepper. Stir and then let green beans cook undisturbed for 5-8 minutes until beans start to get brown and charred.
Once beans start to get brown and blistered, give the beans a good stir and cook 3-4 minutes longer, until mostly tender.
Once beans are blistered and tender, add onions back to the pan. Stir and then spread the vegetables out in the pan in an even single even layer.
Sprinkle over 1/4 cup of the feta cheese.
Pour egg mixture into the pan and gently stir to make sure eggs are distributed evenly. Let eggs set up in pan for about 1 minute.
Sprinkle remaining feta over the top. Carefully transfer pan to preheated oven and bake for 10-15 minutes! Keep and eye on it, eggs cook quickly!
Frittata is ready to come out when it’s puffy, set,and still a little jiggly I’m the center.
Remove frittata from oven, transfer to a cooling rack and let cool about 5-10 minutes before serving.
Serve with sides of your choice and enjoy!