Extract the meat from boiled crabs and mince it finely. Season well with mustard, cayenne, salt, and some sharp sauce. Toss and stir till well mixed, and cook in a covered saucepan, with just enough water to keep the meat from burning. For dressing, use pulverized cracker, moistened with a tablespoonful of cream, and with vinegar until thin. After the water has come to a boil stir this in. Next stir in a tablespoonful of butter, boil again, and take from the fire. Serve in the shell of the crab, if desired.