Clean and wash spinach well. Chop spinach finely and wilt in a little water. Drain well in a colander. Warm olive oil in a pot and lightly sauté leeks and onions. Add spinach. Stir lightly, add dill and other herbs. Turn off heat and set aside to cool. Add feta cheese cut into very small pieces, grated kefalograviera, lightly beaten eggs, pepper and very little salt. Grease a small baking dish and place a layer of puff pastry. Add the spinach filling and cover with another layer of puff pastry. Brush the top with a little milk and ½ cup of soda water. Using a sharp knife score pie and bake for 45 minutes at 180oC.