01 - Preheat oven to 400°F and line a baking sheet with parchment paper.
02 - Heat olive oil in a skillet over medium heat. Add onion and cook for 3–4 minutes until softened. Add garlic and cook for an additional 1 minute.
03 - Add spinach to the skillet and cook until wilted or heated through if using frozen. Remove from heat and allow to cool slightly.
04 - In a mixing bowl, combine the cooled spinach mixture with crumbled feta, dill, nutmeg, one egg, salt, and pepper. Stir until evenly blended.
05 - Roll out the puff pastry on a floured surface and cut into eight equal squares or rectangles.
06 - Place a generous spoonful of filling onto the center of each pastry square. Fold over to form triangles or rectangles and press edges firmly to seal. Crimp edges with a fork.
07 - Arrange pastries on the prepared baking sheet and brush the tops with beaten egg.
08 - Bake for 20 to 25 minutes until pastries are puffed and golden brown.
09 - Allow the pastries to cool slightly before serving.