01 - Preheat oven to 400°F and line a baking sheet with parchment paper.
02 - Heat olive oil in a skillet over medium heat. Sauté onion for 3–4 minutes until softened, then add garlic and cook for 1 minute more.
03 - Add spinach and cook until wilted or heated through if frozen. Remove from heat and allow to cool slightly.
04 - Combine spinach mixture, crumbled feta, dill, nutmeg, 1 egg, salt, and pepper in a bowl. Mix thoroughly.
05 - Roll out puff pastry on a lightly floured surface and cut into 8 equal squares. Place filling in center of each square, fold over to form triangles or rectangles, and seal edges by pressing and crimping with a fork.
06 - Arrange pastries on prepared baking sheet and brush tops with beaten egg. Bake for 20–25 minutes until golden brown and puffed.
07 - Allow pastries to cool slightly before serving.