Cook the gooseberries with the sugar, cordial and measured water in a covered saucepan for 10 minutes until soft. Purée the gooseberries and their cooking juices in a liquidizer or food processor until smooth, or rub through a sieve. Leave to cool.
Whip the cream until it forms soft swirls, then fold in the custard and gooseberry purée. Spoon into small glasses and chill.
Heat the butter, sugar, syrup and lemon rind and juice for the biscuits in a small saucepan until the butter has melted and sugar dissolved. Stir in the flour and bicarbonate of soda and mix until smooth.
Drop teaspoons of the mixture on to 2 greased baking sheets, well spaced apart, then bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 10–12 minutes until browning around the edges. Cool for 10 minutes, then loosen and transfer to a wire rack. Dust with sifted icing sugar and serve with the fool.