This recipe is based on the traditional Charentaise method for baking potatoes or chestnuts in an unglazed potbellied earthenware vessel with a lid called a diable. When cooking wet ingredients such as clams, Charentaise cooks line their unglazed casseroles with leaves (grape, sorrel, or chard) to protect the pot from absorbing shellfish odors and moisture.
I’ve found that a Chinese sandpot makes a great substitute, closely mimicking the diable cooking style. Because the pot has a thin interior glaze, no protection is necessary, but still, for extra fragrance, I line the sandpot with slices of fennel as well as sorrel leaves.
I picked up this truc years ago from a home cook on the Ile de Ré in France. The sorrel not only adds flavor but also has a tenderizing effect on clams. In the Charentes, around La Rochelle, cooks use a variety of clams called amandes de mer (“almonds of the sea”), which have a slightly nutty flavor. I’ve had great success using American littlenecks. Serve this fine starter with the broth enriched with a little melted butter.