Preheat the oven to 200C, 180C fan, gas 6. Line a baking sheet with greaseproof paper.
Open the Pain au Chocolate can. Unroll the dough and cut along the perforated lines. Lay 2 of the rectangles crossing over each other by 2cm on the short end. Place the next 2 in the same way, just underneath and the following 2. You should now have a rectangle.
Slice each of the pastry pieces into 2, cutting just close to where the peanut butter begins. This should give you 12 strips which you can then fold over to create a plait. Take a strip of pastry on the top left and bring it across the peanut butter, repeat with a strip from the top right. Work your way down the pastry until you have a plaited pattern and all the lengths of pastry have been crossed. Seal the ends and brush with beaten egg.
Cook in the oven for 10-15 minutes, until golden and cooked through.
Remove from the oven and let cool. Drizzle with chocolate and serve in slices.