Preheat an oven to 350 degrees F (175 degrees C). Grease a deep 9x9 inch baking dish.
Beat the eggs in a mixing bowl, then stir in the spinach, leeks, green onions, feta cheese, parsley, dill, spearmint, sugar, milk, and 3/4 cup of olive oil until evenly mixed. Season to taste with salt and pepper; set aside. Whisk together the all-purpose flour, semolina flour, and 1 pinch of salt in a mixing bowl. Stir in 1/4 cup of olive oil and the water until no lumps remain. Pour 2/3 of the batter into the prepared 9x9 inch pan, and spread out evenly. Spoon the spinach filling over the batter, then spoon the remaining batter overtop. Sprinkle with the Parmesan cheese, butter pieces, and 2 tablespoons of olive oil.
Bake in the preheated oven until the bottom crust and top has firmed and nicely browned, about 1 hour.