Preheat your oven to 180°C/350°F.
Line your baking sheet with parchment paper.
Unroll or roll out your puff pastry and cut out four squares, approximately 10 cm (4 inches) on each side. Gather the pastry scraps together to form two more small cakes. Place them on the parchment paper.
In the center of each pastry square, place two heaped tablespoons of béchamel sauce, then top with half-rounds of goat cheese, cut lengthwise.
Fold the four corners of the puff pastry over the cheese. Repeat for each pastry.Using a pastry brush, brush the pastries with the egg yolk and cream mixture. Bake for 20 to 25 minutes, until golden brown.Serve warm with a green salad.