Preheat the oven to 400°F (200°C) and prepare a baking sheet lined with parchment paper.

Unfold the thawed puff pastry and cut into 12 equal squares, placing them on the baking sheet.

In a mixing bowl, combine cream cheese, granulated sugar, egg yolk, and vanilla extract, and beat until smooth.

Spoon about 1 teaspoon of filling onto each pastry square, optionally adding fruit preserves on top.

Fold the corners of the pastry squares inward and brush the edges with beaten egg.

Bake for 15-18 minutes until golden brown; watch closely at the end.

Cool briefly on the baking sheet, then transfer to a wire rack. Drizzle with icing if desired.