Prepare the blueberry filling at least a day ahead. Cook the blueberries with sugar until they burst, strain, and refrigerate.

Preheat oven to 400°F (200°C). Roll out puff pastry to a 10x10 inch square and cut into 4 equal squares.

Soften cream cheese at room temperature for 15-20 minutes. Mix in sugar if desired.

Spoon 2 tablespoons of cream cheese into the center of each pastry square, followed by 2 tablespoons of blueberry filling and fresh blueberries.

Freeze assembled pastries for 15 minutes. Prepare egg wash and brush edges. Bake for 20 minutes or until golden brown.

Allow to cool for a few minutes, dust with icing sugar, and serve warm.