Puree the blackcurrants by passing them through a sieve or placing them in a blender and add the lemon juice and/or zest.
To make the fool, beat the cream into soft peaks, being careful not to overbeat. Fold two-thirds of the puree into the cream, add the sugar and mix lightly. Taste and add more sugar if necessary.
Place a few blackcurrants in the base of the glasses, then spoon in alternate layers of the puree and the fool. Fill until the glasses are topped up. Decorate with a few blackcurrants or strawberries and a sprig of mint.
Preparation time approximately 30 minutes.