Preheat the Oven: Preheat your oven to the temperature specified on the puff pastry package.

Prepare the Cream Filling: In a saucepan, whisk together the egg, sugar, cornstarch, and vanilla sugar.

Gradually add the milk while whisking continuously to avoid lumps.

Place the saucepan over medium heat and cook the mixture, stirring constantly, until it thickens.

Remove the saucepan from the heat and stir in the butter until melted.

Prepare the Puff Pastry: Roll out the puff pastry sheets and cut them into squares.

Place a spoonful of the milk mixture onto each puff pastry square.

Top the milk mixture with a slice of peach from the syrup.

Assemble the Pouches: Fold the corners of the puff pastry squares over the peaches to create a pouch.

Place the pastries on a baking sheet lined with parchment paper.

Bake: Bake in the preheated oven for about 15-20 minutes, or until the pastries are golden brown.

Serve: Remove from the oven and let cool slightly before serving.