Work very, very quickly with filo (phyllo) sheets. And make sure they're thawed.
1/3 cup olive oil
1 small fennel bulb, trimmed and finely chopped 
1 leek (white part plus three inches of the green part), finely chopped 
1/2 cup chopped onion
5 scallions (white and most of the green bits) sliced in thin rounds
1 pound spinach, coarsely chopped 
1 cup coarsely chopped fresh flat-leafed parsley 
1/2 cup coarsely chopped fresh dill
salt and freshly ground black pepper
8 oz sheep's milk feta 
1/2 package frozen filo (Phyllo) pastry
2 sticks of butter
In a large skillet, heat the oil and saute the fennel, leek, and onion for 4 minutes, or until soft. Add the scallions and saute for a minute, then add the spinach and stir frequently until they wilt. Stir in parsley and dill and cook until wilted. Remove from heat, sprinkle with pepper and a small amount of salt, and let cool.
Add feta and eggs to the spinach mixture. Melt the butter. Get ready for the filo.
Clean a large section of countertop or table, and cover with plastic wrap. Dampen a hand towel. Open the thawed filo pastry slowly, and lay it out on wax paper so that you can get one sheet at a time off of the stack. Take one sheet and move it to the plastic wrapped area. Cover the remainder of the filo with plastic wrap and the damp towel. Don't let the towel touch the pastry.
Brush the sheet with butter, then lay another sheet of filo on top. Brush it with butter. Using a sharp knife, cut the sheets lengthwise in three inch sections. Place a spoonful of spinach and cheese mixture on a filo section, about two inches from the end of the sheet, and fold the filo like a flag, ending with a triangular pie.
Bake at 350F for about fifteen minutes.
 Fennel bulbs are frequently mis-labeled in grocery stores as "anise". Look for a celery-like stalk with a white bulb on the end.
 Leeks are difficult to clean. Soak them in water for about a half-hour to get all the dirt loosened from inside the leaves. Alternately, wash the rings after chopping them.
 Pick through the spinach, tear off all the stems, and tear into small pieces. Chopping spinach sucks. You could also use thawed, frozen chopped spinach.
 Curly parsley doesn't have near enough flavor. Flat is the way to go, but make sure it's not cilantro. They smell different.
 Sheep's milk feta has a much richer taste, and, I think, melts better.