Melt the butter or margarine and syrup in a saucepan, then remove from the
heat and stir in the cereal. Press the mixture into a 20 cm/8 in pie dish
and chill. Put the marshmallows, hot water and coffee powder into a bowl
over a pan of hot water. Simmer until the marshmallows have melted,
stirring occasionally, then leave to cool. Fold the cream into the coffee
mixture with two sliced bananas. Cool until thick, then pour on to the
crisp base and chill until firm. Decorate with the remaining banana.