Remove crab meat from shell, discarding cartilage, then finely chop all of crabmeat and transfer to a bowl. Melt butter in a 10-inch heavy skillet over low heat and stir in remaining ingredients (except crabmeat). Cool 3 minutes, then stir in crabmeat.
Transfer mixture to 4 to 6 individual serving ramekins and tamp down. Cover the surface of each ramekin with a circle of wax paper, then cover the dishes with plastic wrap and chill at least 2 hours, preferably overnight.