Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.

In a large mixing bowl, combine the chopped spinach, softened cream cheese, grated Parmesan cheese, minced garlic, salt, and black pepper. Mix until well combined.

On a lightly floured surface, roll out one sheet of puff pastry into a rectangle. Cut the pastry into squares, approximately 3×3 inches in size.

Place a spoonful of the spinach and cream cheese mixture in the center of each pastry square.

Fold the corners of each pastry square towards the center, pinching the edges to seal and form a puff.

Repeat the process with the remaining puff pastry sheet and spinach mixture.

Place the assembled spinach puffs on the prepared baking sheet. Brush each puff with the beaten egg and sprinkle with sesame seeds or poppy seeds, if desired.

Bake in the preheated oven for 15-20 minutes, or until the puffs are golden brown and puffed up.

Remove from the oven and let cool slightly before serving.