Preheat oven to 400 degrees F. Line two baking sheets with parchment paper or silicone baking mats.

Lay one sheet frozen puff pastry on a lightly floured work surface to thaw for 10 minutes.

Meanwhile, prepare the cream cheese filling: Using an electric mixer, beat together the cream cheese, yogurt, egg yolk, granulated sugar, vanilla, and lemon zest until smooth.

Cut puff pastry into 12 to 16 equal rectangles. Place the puff pastry pieces on the prepared baking sheet.

Use a sharp knife to score a smaller rectangle into each piece, about ½-inch from the edge. Do not cut all the way through the pastry. Use a fork to poke several holes inside the inner rectangle. Do not poke any holes in the ½-inch border. These two steps will allow the outside edges of the pastries to puff up while baking, while preventing the middle from puffing so it can hold the filling.

Spoon about 1 tablespoon of the cream cheese filling in the center of each pastry piece and spread it out over the middle of the dough, leaving the ½-inch border free of filling. Top cream cheese mixture with a few blueberries.

Make the egg wash by beating together the egg white and tablespoon of water with a fork. Brush the outer ½-inch border of each pastry with the egg wash.

Bake pastries for 12-14 minutes, until pastry is lightly golden. Let cool for 10 minutes before glazing.

Once the pastries are cool, make the glaze: Whisk together the powdered sugar, heavy cream, and pinch of salt. Drizzle the glaze over the tops of the pastries. (You can either do this with a spoon or by placing the glaze in a small zip-top plastic baggie and cutting off a very tiny piece of the corner to pipe the glaze.) Serve, topping with additional blueberries if desired. Refrigerate any leftovers.