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

In a mixing bowl, combine the cream cheese, granulated sugar, egg yolk, and vanilla extract. Beat with an electric mixer for 2-3 minutes until smooth.

On a lightly floured surface, roll out the puff pastry to about 1/8-inch thick and cut into 12 equal squares.

Spoon about 2 tablespoons of cream cheese filling onto the center of each square, fold the corners towards the center, and pinch edges to seal.

Whisk the remaining egg and brush it evenly over the tops of each filled puff.

Bake in the preheated oven for 20-25 minutes until golden brown.

Cool on a wire rack for 5 minutes, then dust with powdered sugar before serving.