Melt half chopped chocolate over hot water, spread over base of well-greased tin, refrigerate.
Put butter, sugar and dates in saucepan; cook, stirring, until dates are soft.
Stir in sufficient Rice Crispies to make a firm but spreadable mixture, and spread over chilled chocolate.
Melt remaining chocolate, spread over as a topping; refrigerate until firm.
Cut into small squares.