On a floured surface roll out the puff pastry to 1cm thickness.
Prepare a buttered baking tray, place the puff pastry on the tray.
Take out your whole side of salmon and season with salt and pepper.
Place the salmon on the puff pastry and spread the pesto generously on the flesh side of the Salmon.
Now fold the puff pastry over the fish starting with the longer side and close the salmon like a parcel.
Fold in the edges and turn it over.
Place the whole "parcel" on the prepared baking tray. Make crosshatch slits on top of the salmon with a knife.
Brush with egg yolk and place in a preheated 200°C oven for 30 to 45 minutes until golden brown.
Take out of the oven cover with aluminum foil and let it rest for 30 minutes.
Serve on a large plate or a cutting board.