Preheat your oven to 375°F (190°C) and let the puff pastry thaw at room temperature for about 30 minutes.

In a large bowl, combine the frozen spinach, cream cheese, mozzarella, and parmesan, adding garlic and onion powder. Mix until creamy.

Roll out the thawed puff pastry to about 1/8-inch thickness and cut into 3x3 inch squares.

Place about one tablespoon of filling in the center of each square, fold corners to seal, and crimp with a fork.

Brush tops with egg wash or milk for a golden finish.

Bake on a lined sheet for 15-20 minutes until golden brown.

Let cool for a few minutes before serving. Enjoy warm!