Tuna triangle

Sprinkle the gelatine over the cold water and leave for a few minutes. Add the chicken stock and heat over boiling water or in the microwave oven until the gelatine has melted. Do not allow the mixture to boil. Add the remaining ingredients except the water biscuits, and mix lightly. Arrange three rows of five biscuits each on a large piece of aluminium foil and spread with half the fish mixture. Add another layer of biscuits and spread the rest of the fish mixture over. Using the aluminium foil, fold the outer two rows of biscuits to the inside so that a triangle is formed. Wrap well in the aluminium foil and chill until firm.
Makes 20 thick slices.