Making Flaky Spinach Puffs with Cream Cheese Filling is a straightforward process if you follow these simple steps:

1. Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
2. Prepare the filling: In a mixing bowl, combine the chopped spinach, softened cream cheese, mozzarella, Parmesan, minced garlic, onion powder, salt, and pepper. Mix until well blended.
3. Roll out the pastry: On a floured surface, roll out one sheet of thawed puff pastry into a large rectangle, about 1/8 inch thick.
4. Cut the pastry: Using a sharp knife or pizza cutter, slice the dough into squares that are about 3 inches by 3 inches.
5. Add the filling: Place a tablespoon of the spinach and cream cheese mixture in the center of each pastry square.
6. Seal the puffs: Fold the pastry over the filling to form a triangle. Press the edges together firmly to seal. You can use a fork to crimp the edges for extra reinforcement.
7. Prepare the egg wash: In a small bowl, whisk the egg until smooth. Brush the egg wash over the tops of each pastry to give them a golden color while baking.
8. Sprinkle sesame seeds: If desired, sprinkle sesame seeds on top of each puff for added texture and flavor.
9. Bake: Place the puffs on the prepared baking sheet and bake for 25-30 minutes or until they are golden brown and puffed up.
10. Cool: Once done, remove from the oven and let cool for about 5-10 minutes before serving.

This easy-to-follow recipe ensures that you achieve delectable Flaky Spinach Puffs every time!