For the fresh mayonnaise, put 2 yolks in a bowl with the mustard and vinegar and mix well with a whisk, now stir in the oil little by little until you get a firm mayonnaise. Season with salt and pepper and add finely chopped parsley.
First rinse the whelks carefully under running water to remove all the sand and dirt. Put the whelks in the stock and bring to the boil. When it reaches boiling point, continue to simmer the whelks over a low heat until they are cooked (about 15 to 20 minutes in total). Leave them to cool in the cooking liquid.
Remove the whelks from the shells with tweezers and skewer each 3 pieces with 2 skewers. Grill them over the hot Binchotan until they begin to colour.
Serve the whelks with the parsley mayonnaise.