200g caster sugar 200g softened butter 4 eggs, beaten 200g self-raising flour 1 tsp baking powder 2 tbsp milk 100g butter, softened 140g icing sugar, sifted drop vanilla extract (optional) 340g jar good-quality strawberry jam ( we used Tiptree Little Scarlet) icing sugar, to decorate Want to see what this recipe costs at different supermarkets?