Blend the cornflour with a little of the milk.

Heat the remaining milk and stir into the cornflour mixture, then return to the saucepan. Heat, stirring continuously until the mixture thickens. Cook for 1 minute. Add sweetener to taste and leave to cool.

Trim and wash the blackcurrants, then put in a pan with the water. Cook gently until the fruit is soft. Add sweetener to taste and leave to cool. Puree the fruit in a blender or rub through a sieve.

Add the fruit puree and yogurt to the sauce and whisk until well blended. Spoon into four individual serving dishes and decorate with blackcurrants. Chill before serving.

If possible, use a blender to puree the blackcurrants rather than rubbing the fruit through a sieve as this reduces the fibre content which is mostly in the seeds.