Preheat the oven to 400°F. Line 2 large baking sheets with parchment paper and set aside.
Lay the puff pastry sheets on a lightly floured surface, and cut each sheet into 6 equal-sized rectangles. You will have a total of 12 rectangles, about 4½x3 inches in size.
Arrange the puff pastries evenly onto the lined baking sheets, leaving about 1 inch between each pastry.
Use a fork to poke holes around the middle where you will be putting the filling Do not poke holes near the outside, creating a border. This allows the outside border to rise and puff up while the center stays low and holds the filling.
In a small bowl, combine the cream cheese, sugar, lemon juice, and vanilla extract.
Spread about 1 tablespoon of cream cheese mixture onto the center of each puff pastry.
In a small bowl, mix together blueberry jam and the fresh blueberries.
Top the cream cheese mixture with the blueberry mixture.
In a small bowl, whisk egg. Brush onto outside edges of pastry.
Bake for 15- 18 minutes, or until golden.
Remove from oven. Set aside to cool slightly.