Preparing the Filling​

1. Sauté the Vegetables: 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.
2. Add Spinach: 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.

Mixing the Cheese Filling​

1. Combine Cheeses: In a large mixing bowl, combine 1 cup of ricotta cheese, 1 cup of crumbled feta cheese, and 1/2 cup of grated Parmesan cheese.
2. Add Egg: 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.

Assembling the Pie​

1. Prepare the Crust: 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.
2. Fill the Crust: Spoon the spinach and cheese filling into the prepared crust, spreading it evenly.
3. Seal the Pie: 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.

Baking the Pie​

1. Preheat the Oven: Preheat your oven to 190°C.
2. Egg Wash: Beat 1 egg and brush it over the crust to give it a golden color when baked.
3. Bake: 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.
4. Cool and Serve: Allow the pie to cool for about 10 minutes before slicing. Serve warm or at room temperature.