You don’t have to use Greek yogurt in your spanakopita, but there’s something about it that 1) just seems right, and 2) adds a little extra moisture to the mixture. This recipe almost makes it feel like a Greek spinach chicken pot pie (sans chicken, obviously).
Preheat the oven to 400 degrees and thaw the pastry if it’s frozen. Steam the spinach, then drain it — try to remove as much moisture as possible by either rolling it in paper towels or a clean dish towel. After finely chopping the spinach, add finely chopped white and green onions, dill, a half-container of yogurt, ½ pound of feta, and 4 beaten eggs. Mix well and adjust seasoning.
Use olive oil to prime your container, then line the bottom with one portion of the pastry. Evenly distribute the spinach and feta mixture over the pastry, cover that with the rest of the yogurt, scatter the rest of the feta evenly over that, and then finish it off by covering the filling with another piece of pastry.
Brush it with a beaten egg and put it in the oven for a half-hour at 400 degrees. Remove, allow it to set for a few minutes, and then dig in!