1 small yellow onion, finely chopped
2 garlic cloves, minced
1/2 stick unsalted butter
10 ounces frozen chopped spinach, thawed
Sea salt and freshly ground pepper
6 ounces crumbled feta cheese
8 ounces shredded Parmesan or gruyere
1 (9–inch) frozen deep-dish pie crust (preferably whole grain)
½ cup milk
Preheat the oven to 375 degrees Fahrenheit.
In a medium skillet, sauté the onion and garlic in butter over medium heat, about 8 minutes. Add the spinach, season with salt and pepper, and cook for 5 minutes. Mix in the Feta and half the Parmesan and transfer into the piecrust.
In a bowl, whisk the eggs with the milk and season with salt and pepper. Gently pour the milk and egg mixture on the quiche, poking little holes in the spinach with a fork to help the liquid penetrate.
Carefully transfer the quiche into the oven. Bake for 15 minutes. Top the quiche with the rest of the parmesan and bake for 30 minutes.