Cut 4 bars of chocolate (approx. 80 g) into small pieces. Cut chocolate shavings from a bar with a peeler. Melt the remaining chocolate on a hot water bath.
Unroll the puff pastry with the baking paper on a baking tray and cut into 8 cake pieces. Place the chocolate pieces on the wide parts of the triangle and roll up into croissants. Whisk egg yolk and cream and spread on the croissants.
Bake in the preheated oven (electric oven: 200°C/ gas: level 3) for 15-20 minutes. Cover at the end of the baking time if necessary. Put melted chocolate in a freezer bag and cut off a small corner.
Spray strips over the cooled croissants and sprinkle with chocolate shavings. Makes 8 croissants.