A savory Greek pastry filled with spinach, eggs, cheese, and herbs. This recipe utilizes puff pastry, but you could easily use the same filling for a version with phyllo dough instead.
Pre-heat the oven to 375°F.
Heat 2 tsp. of the oil in a 12-inch skillet over medium-high heat. Add a batch of spinach and toss with tongs until just wilted, about 2 minutes. Transfer spinach to a colander set over a bowl. Allow to drain. Repeat with the remaining spinach. You may add a tiny bit of oil as needed, but be careful not to over do it as you don't want to be left with oily spinach. This will make your pastry soggy.
Wipe the pan, reduce the heat to medium, and add the remaining 2 Tbs. oil. Add the onion and scallions and cook until softened, about 4 minutes. Add the garlic and cook, stirring, for 1 minute. Remove from the heat and let cool.
In a large bowl, lightly beat 3 whole eggs. Season with a generous pinch of salt, pepper, and the grated nutmeg. Stir in the dill, parsley, and both cheeses.
Squeeze handfuls of the spinach to release as much liquid as possible; then separate the clumps with your fingers. Add the spinach and the onion mixture to the eggs and stir to combine.
Line 2 baking sheets with parchment paper. Before unfolding, cut each puff pastry sheet into thirds crosswise. Unfold each third of pastry and cut each into thirds again.
Using a lightly floured work surface, roll half of the puff pastry pieces into a 4 inch square, and the other half into a 5 inch square. The larger squares will be used for the tops of the spanikopita.
Whisk the egg yolks together with 2 tsp. water in a small bowl. Lightly brush the borders of the 4-inch pastry squares with egg wash. Place 1/2 cup of filling or less if needed in the center of each pastry square. Spread filling flat, leaving a 1/2 inch border around the filling.
Place a 5-inch pastry square over each of the bottom halves with filling. Using the prongs of a fork, carefully crimp the edges of the top and bottom pastry squares together to create a seal.
Brush the top of each pastry with egg wash. Cut a small X as a steam vent on atop the center of each pastry. Brush the top of each pastry with the remaining egg wash and cut a small vent to allow steam to escape. Bake, swapping and rotating the baking sheets’ positions halfway through baking, until a knife inserted into the filling comes out clean and the pastry is puffed and deep golden, about 20 minutes.
Allow to cool on baking sheet for 10 minutes, then cut each square in half diagonally. Serve.
Letting the puff pastry come all the way to room temperature before cutting and rolling it out will result in a flatter cooked pastry. If you prefer a puffier pastry, cut and roll out the pastry dough shortly after the dough is taken out of the freezer or as thawed according to package directions.