Blend the cornflour with a little cold milk. Boil the rest of the milk with the thinly cut lemon rind. Strain the boiling milk on to the blended cornflour and stir well. Rinse the pan and return the sauce to it. Just bring to boil for custard powder, boil 3 min. for cornflour, then add the lemon rind, sugar or golden syrup to taste, stir in the lemon juice.