2 (10 oz.) pkgs. frozen, chopped spinach, thawed and drained
1 c. butter
2/3 c. onion, chopped
8 oz. Mozzarella cheese
1 3/4 c. (15 oz.) Ricotta cheese
4 eggs, slightly beaten
1 tsp. salt
1/4 tsp. pepper
12 sheets filo or strudel dough

Squeeze spinach dry on paper towels. In skillet, melt 2 tablespoons butter; add onion and saute over medium heat until soft, about 2 or 3 minutes. Set aside to cool. Add cheeses, eggs, salt and pepper to spinach mixture. Stir until well mixed.

Preheat oven to 350 degrees. Melt remaining butter. Cover bottom of 9x13 inch pan with 6 sheets (leaves) filo dough, brushing each sheet lightly with melted butter. (Trim sheets if necessary.) Spread evenly with spinach mixture. Cover with 6 more sheets of filo dough, again brushing each sheet lightly with melted butter. To retain filling, seal edges by tucking them under with a spoon. With a sharp knife, cut through filo layer to spinach. Brush top with any remaining butter. Bake for 45 minutes until golden.