Creating Spinach Dip and Cheese Bites is a delightful adventure. Follow these steps for a flawless preparation:

1. Preheat Oven: Start by preheating your oven to 400°F (200°C).
2. Prepare Spinach: In a large bowl, combine the chopped spinach and minced garlic. Mix thoroughly.
3. Add Cheeses: Next, add the softened cream cheese, shredded mozzarella, and grated Parmesan to the spinach mixture. Stir until everything is well combined.
4. Season: Add onion powder, salt, and black pepper to the cheese and spinach mixture, blending until evenly mixed.
5. Roll Out Puff Pastry: Unroll the refrigerated puff pastry sheets on a lightly floured surface. Cut them into 3-inch squares.
6. Fill Pastry Squares: Spoon a generous amount of the spinach and cheese mixture into the center of each pastry square.
7. Seal Bites: Fold the corners of the pastry squares over the filling, pinching them together to create a pocket. Ensure there are no leaks.
8. Prep for Baking: Place the sealed bites on a baking sheet lined with parchment paper. Brush the tops with the beaten egg for a golden finish.
9. Bake: Bake in the preheated oven for 20-25 minutes, or until the pastry is puffed and golden brown.
10. Cool: Once baked, remove from the oven and allow them to cool on the baking sheet for about 10 minutes before transferring to a serving platter.

These simple steps will lead you to a batch of delicious Spinach Dip and Cheese Bites that will surely impress anyone who lays eyes (and taste buds) on them.