1 frozen unbaked 9-inch deep-dish pie shell
4 Tbs. unsalted butter
2 Tbs. olive oil
3 large Vidalia onions (about 1½ lbs.), thinly sliced
4 large eggs, lightly beaten
8 oz. sour cream
Dash hot sauce
1 tsp. kosher salt
1/2 tsp. ground white pepper
1 cup plus 1/4 cup grated sharp cheddar cheese (organic sharp cheddar grated by hand preferred), divided
1/4 cup grated Parmesan cheese
Preheat the oven to 425°F.
Set the frozen pie shell on the counter to thaw while preparing the ingredients. Heat the butter and olive oil in a large skillet over medium heat. Add the onion slices and saute them until well softened, about 10 minutes. While the onions cook, combine the eggs, sour cream, hot sauce, salt, and pepper in a large bowl and combine well with a whisk. Add one cup of the cheddar cheese.
When the onions are soft, use a slotted spoon to transfer one spoonful of onions into the egg mixture at a time, stirring after each addition to ensure that the eggs do not scramble. When all onions are added, gently pour the mixture into the unbaked pie crust.
Place the pie on a rimmed baking sheet and put it into the oven. Bake it at 425°F for 20 minutes, then reduce the oven temperature to 325°F and bake for an additional 15 minutes. Take the pie out of the oven, sprinkle on the remaining cheddar and the Parmesan cheese, and bake for eight to 10 more minutes, until the cheeses have melted and are lightly browned. Ensure that pie is set by inserting a knife into its center. Allow to cool for five minutes before slicing.