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

Prepare the Cream Cheese Filling: In a medium bowl, mix the softened cream cheese, powdered sugar, and vanilla extract until smooth and creamy.

Prepare the Blueberries: In another bowl, combine the blueberries, granulated sugar, and lemon juice. Toss gently to coat the blueberries.

Roll Out the Puff Pastry: On a lightly floured surface, roll out the puff pastry sheet to smooth it out. Cut it into 8 equal squares (about 4x4 inches each).

Assemble the Pastries:

Place about 1 tablespoon of cream cheese filling in the center of each pastry square.

Top with a spoonful of the blueberry mixture.

Fold the corners of the pastry square towards the center, pinching to seal, or leave them open for a more rustic look.

Brush with Egg Wash (Optional): If using, beat the egg and brush it over the tops of the pastries for a golden finish.

Bake: Place the pastries on the prepared baking sheet and bake in the preheated oven for 20-25 minutes, or until golden brown and puffed.

Cool and Serve: Allow the pastries to cool slightly before serving. Optionally, dust with powdered sugar for added sweetness.