Preheat your oven to 375°F (190°C). Unroll your pre-made pie crust and gently fit it into a 9-inch pie dish. If you’re using homemade, prepare and press your dough into the dish. Prick the bottom of the crust several times with a fork. You can blind bake the crust for 10-15 minutes if you prefer a crispier bottom.
Heat the olive oil in a large skillet over medium heat. Add the finely chopped onion and cook until it’s beautifully softened and translucent, about 5-7 minutes. Stir in the minced garlic and cook for just another minute until it becomes wonderfully fragrant – don’t let it brown!
Add your roughly chopped fresh spinach to the skillet. Cook, stirring frequently, until the spinach has completely wilted and any excess moisture has evaporated.
In a large bowl, combine ricotta cheese, grated Parmesan cheese, freshly grated nutmeg, and a generous pinch of salt and pepper. Add the cooked spinach mixture to this bowl and stir everything together until it’s perfectly combined.
In a separate medium bowl, whisk together the eggs, milk, and heavy cream until they are light and well combined.
Spoon the spinach and ricotta mixture evenly into your prepared pie crust. If you’re using it, sprinkle the shredded mozzarella evenly over the spinach mixture.
Slowly and carefully pour the egg mixture over the top, making sure it distributes evenly throughout the filling.
Carefully transfer the pie dish to your preheated oven. Bake for 45-55 minutes, or until the center is set (a knife inserted into the center should come out clean!) and the top is a beautiful golden brown. If the edges of your crust start to brown too quickly, you can loosely cover them with a strip of aluminum foil.
Once baked, remove the quiche from the oven and, I know it’s hard, but let it cool for at least 10-15 minutes before slicing and serving.