To make the sauce, blend the cornflour with 2 tablespoons of the milk in a saucepan with a wooden spoon. Add the remaining milk, bring to the boil and cook for 2 minutes until thickened.
Stir in the low-fat spread, vanilla essence and sugar. Leave to cool.
Keeping half an apricot aside for decoration, purée the rest with the juice in a blender or food processor. Fold into the sauce.
Spoon into individual glasses, and chill for 1 hour before serving.