Boil the shanks. Place the shanks in a cauldron or deep saucepan. Add onion, carrot, bay leaves, salt and black peppercorns. Cover with water and cook for 1.5-2 hours until the meat is soft, skimming off the foam. Do not drain the broth after cooking.
Make the jellied meat. Remove the shanks and vegetables from the broth. Cool the shanks a little, remove the skin and meat. Remove the fat and skin - you won't need them. Cut the boiled vegetables into circles and place them in a mold with the meat. Strain the warm broth through a fine-mesh sieve. Add gelatin and leave to swell for 5 minutes. Stir until completely dissolved. Pour the broth over the meat and vegetables. Garnish the dish with parsley. Place the jellied meat in the refrigerator for 1 hour to set.