Defrost Puff Pastry:
Defrost the puff pastry sheet per the package directions.Preheat Oven and Prep:
Heat oven to 395°F (200°C) and cover a baking sheet with parchment paper.Mix Cheese Filling:
In a small bowl, combine the farmer cheese, powdered sugar, and vanilla extract until smooth.Roll and Cut Pastry:
On the parchment, lightly roll the pastry to roughly 9x11 inches. Slice into 6 equal rectangles, spacing them about 2 inches apart. Gently score a smaller rectangle 1/4 inch inside each pastry's border without cutting through.Add Filling and Blueberries:
Distribute the cheese mixture over the inner rectangles, then arrange a single layer of blueberries on top.Brush Egg Wash:
In a small bowl, whisk the egg. Brush the egg wash onto the outer edges of each pastry.Bake Until Golden:
Place on the middle oven rack and bake until the edges turn golden, about 15-20 minutes.Cool and Dust Sugar:
Allow to cool for 5-10 minutes. Dust with additional powdered sugar and serve.