Open up puff pastry on a well-floured work surface.
Gently roll each piece, divide into 4 parts with a knife, and from each part cut 2 triangles.
In one triangle put a teaspoon of pastry cream or cocoa cream.
Roll it from the base of the triangle until the tip.
Brush the surface with beaten white egg and put it into the preheated oven at 180°C(356°F) for about 25-30 minutes.
After, remove the croissants from the oven and sprinkle them with powdered sugar.