San Francisco Clambake with Instan Clam Broth

If we had to pick our favorite shellfish recipe, this would win, hands down. The idea is borrowed from the New England clambake: a large pit is dug at the beach and filled with hot stones, then topped with damp seaweed. Into this steamy pit is dumped layers of lobsters, clams, scampi, oysters, scallops, mussels-all in the shell-and sometimes topped with potatoes and ears of sweet corn in the husk. When all these goodies get steamed together, the result is one of the loftiest feasts since ma