Wash the spinach and dry overnight. Discard stems. Chop spinach and onions. Add crumbled feta and beat eggs. Season to taste, Pour half the melted butter over spinach and toss lightly to combine ( I normally omit the butter but it does taste better with it )
Brown 4 sheets of pastry in an oven and very carefully set aside.
Set 6 sheets on a greased pan spreading each one with melted butter. Top with one of the four baked sheets and sprinkle with spinach mix.
Mix alternately with phillo, phillo baked sheets, and spinach mix. Covered with 6 buttered phillo sheets.
Use a 10x15 inch pan. Bake at 350 degrees for one hour, after baking 30 minutes remove panfrom over and pour remaining butter over phillo and bake another 30 minutes.