This recipe comes from my maternal Calabrese grandmother. It was traditionally served on Christmas eve and contains only shellfish. Some cioppino recipes include calamari (squid), mussels, and/or chunks of solid bodied fish that holds together during cooking. The two essential ingredients are Dungeness crab and garlic. Note: Live Dungeness crabs are preferred for this dish. If they are not available in your area, cooked and cracked crab may be substituted. If they are, add them after the prawns. You only want to re-heat the crab, not overcook it. Tip: Supply each guest with ample napkins, a bib, and a nutcracker and pick to get at all of the sweet Dungeness crab.