Poach oysters in their own liquor for 2 minutes. Sprinkle sherry over oysters. Clean the bottom of the deeper oyster shells and set them on a baking tray covered with rock salt. Saute chopped celery in butter and place 1 teaspoonful in each shell. Place a poached oyster on each bed of celery and cover with Bechamel Sauce which has been mixed with a few drops of melted butter over each oyster. Bake in a hot 400°F oven until golden brown. Serve with dark bread and butter.