Thaw frozen spinach and squeeze all the water out.
Chop an onion.
Pour 1 tablespoon of olive oil in a skillet and saute for 3-4 minutes.
In a bowl, combine spinach, onions, mozzarella, cream cheese, Parmesan cheese, and 2 eggs. Optional: we sometimes add some shredded chicken, especially if there are leftovers.
Cut puff pastry into small squares, that could fit into a muffin cup.
Fill the muffin cup with the first layer, a square of puff pastry or pie crust.
A melon ball scoop of the cheese and spinach mixture.
Top with a second square of puff pastry or pie crust.
Bake at 400 degrees for 30 minutes, or until it is cooked all the way through.