Preheat your oven to 400°F (200°C) to ensure it's hot and ready.
In a medium skillet, heat the olive oil over medium heat. Once hot, add the minced garlic and sauté for about 1 minute, or until it becomes fragrant and lightly golden.
Stir in the chopped spinach and cook until it wilts, which should take about 2-3 minutes. Season the spinach mixture with salt, freshly cracked black pepper, and a pinch of nutmeg if you're using it.
In a mixing bowl, combine the wilted spinach and garlic with the ricotta, crumbled feta, and grated Parmesan cheese. Stir thoroughly to ensure all ingredients are well mixed and creamy.
On a lightly floured surface, roll out the thawed puff pastry sheet until it's approximately 1/4 inch thick. Cut the pastry into squares or rectangles measuring about 4x4 inches.
Place a generous tablespoon of the spinach-cheese mixture in the center of each pastry square, taking care not to overfill them.
Gently fold the pastry over to create a triangle or rectangle, ensuring to seal the edges tightly by pressing with your fingers or using a fork to create a decorative edge. Brush the tops of the pastries with the beaten egg.
Arrange the stuffed pastries on a parchment-lined baking sheet. Bake in your preheated oven for 20-25 minutes, or until they are golden brown and puffed up delightfully.
Once they’re done, remove the pastries from the oven and let them cool slightly before serving to enhance their flavors.
Notes
Serve warm on a rustic board, garnished with fresh spinach and Parmesan. Pair with marinara sauce for dipping.