In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add 1 finely chopped onion and sauté until translucent, about 5 minutes. Add 2 minced garlic cloves and cook for another minute until fragrant.

Stir in 2 cups of chopped fresh spinach and cook until wilted, about 2-3 minutes. Season with salt and pepper to taste. Remove from heat and let the mixture cool slightly.

In a large mixing bowl, combine 1 cup of ricotta cheese, 1 cup of crumbled feta cheese, and ½ cup of grated Parmesan cheese.

Beat 1 egg and add it to the cheese mixture. Mix well to combine. Then, add the cooled spinach mixture and stir until everything is well incorporated.

If using puff pastry, roll it out on a lightly floured surface to fit your pie dish. If using a pre-made pie crust, simply fit it into the dish.

Spoon the spinach and cheese filling into the prepared crust, spreading it evenly.

If using puff pastry, fold the edges over the filling and crimp to seal. If using a pie crust, place a second crust on top, sealing the edges well. Cut a few slits in the top crust to allow steam to escape.

Preheat your oven to 375°F (190°C).

Beat 1 egg and brush it over the crust to give it a golden color when baked.

Place the pie in the preheated oven and bake for 30-35 minutes, or until the crust is golden brown and the filling is set.

Allow the pie to cool for about 10 minutes before slicing. Serve warm or at room temperature.