Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.

In a medium saucepan, combine fresh blueberries, both sugars, lemon zest, lemon juice, and cornstarch over medium heat. Stir continually until the blueberries burst and the mixture thickens, about 5–7 minutes. Remove from heat and cool.

Beat the softened cream cheese in a mixing bowl until smooth, then add the egg yolk, sugar, vanilla extract, and lemon juice, blending until creamy.

Roll out one puff pastry sheet to ¼ inch thick, spread the cream cheese filling over it, and layer the cooled blueberry mixture on top.

Place the second puff pastry sheet over the blueberry layer, align edges, cut into diagonal strips, and roll each strip into a crescent shape.

Whisk together the egg and water to create an egg wash and brush it over each pastry roll. Bake for 20 minutes until golden brown.

Allow the pastries to cool slightly before dusting with powdered sugar and serving warm.