Preheat: Set oven to 400°F (200°C) and line a tray with parchment.
Sauté: Cook garlic in olive oil for 1 min. Add dry spinach, nutmeg, salt, and pepper. Sauté for 2 mins to remove moisture. Let cool.
Mix: Combine cooled spinach with mozzarella, feta, and parmesan.
Cut: Roll out pastry sheets and cut each into 4 squares (8 total).
Fill: Place 2–3 tbsp of filling in the center of each square.
Seal: Brush edges with egg wash, fold into a triangle, and crimp with a fork.
Top: Brush tops with egg wash and sprinkle with seeds.
Bake: Bake for 20–25 minutes until puffed and deeply golden.