Remove the shells from the langoustes, leave the tail. Make an incision in the middle of the back and pull out the dark vein.
Put the langoustes in this mixture and leave them in the fridge for 30 minutes. Whisk the eggs in a bowl and put the breadcrumbs in another bowl. Take the the langoustes out of the marinade and dry them.
String them up on wooden skewers, dip in egg and then in breadcrumbs. Fry until golden and keep warm with a lid. Boil the marinade over low heat for 6 minutes.
Grate the chocolate and add it to the marinade, let it melt and remove it from the heat. Serve the the langoustes with the marinade and sprinkled with salt.