Preheat oven to 350 degrees. Cook the spinach in boiling water. Drain, rinse with cool water, and squeeze out as much moisture as you can.
Melt the butter in a small skillet. Cook the green onions until slightly soft.
In a large mixing bowl, combine the cheeses and the eggs. Mix well.
Add the spinach, the butter and scallions, the salt and pepper and mix again.
Lightly butter the bottom and sides of an 8-inch square baking dish. Roll out a sheet of puff pastry on a floured surface to make a 14-inch square. Roll out a second sheet to make a 9-inch square. Lay the bigger pastry sheet in the buttered dish, draping the extra pastry over the edges.
Spread the spinach and cheese mixture evenly in the dish. Put the remaining pastry sheet on top. Trim excess pastry if necessary and seal the edges closed. Use scraps of pastry dough to decorate the top of the pie.
Brush top with additional melted butter if desired. Bake for 45 minutes at 350 or until pastry is golden brown. Let rest for 10 minutes before serving.