Add the egg, a little at a time, to the creamed mixture, beating well.
Sift in the flour and fold in lightly. Divide the mixture into two greased and base-lined sandwich tins (18cm/7inch). Bake for 25 minutes until risen and golden brown.
Cool in the tins for about a minute, then turn out onto a wire rack to become cold.
Sandwich the cakes together with the jam and cream (and sliced strawberries/blueberries, if required).
Sift the Golden Icing Sugar all over the top, and decorate with 2 or 3 strawberries or blueberries.