Spinach and Cheese Puff Pastry Squares

Ingredients:

2 sheets of puff pastry (thawed if frozen)

1 ½ cups spinach (chopped and cooked, excess water squeezed out)

1 cup ricotta cheese (or feta for stronger flavor)

½ cup mozzarella cheese, shredded

1 egg (for egg wash + 1 extra for the filling)

Salt and pepper to taste

Optional: Sesame seeds for topping