Preheat oven to 400 degrees Fahrenheit. Grease mini muffin tins with cooking spray.

Cut each square dough in half and press into each muffin hole.

While oven is preheating, prepare spinach filling.

In a bowl, combine spinach, cheeses, and egg, and season well with salt and pepper.

Fill puff pastry squares with spinach-cheese mixture and bake for 15–20 minutes until edges are golden brown.