lemon curd or jam for the topping (optional)
100²µ/3½´Ç³ú caster sugar
200g/7oz icing sugar, sifted
¼ tsp fine salt
100²µ/3½´Ç³ú self-raising flour
1 tsp vanilla extract
100²µ/3½´Ç³ú unsalted butter, softened
125g/4½oz unsalted butter, softened
2 free-range eggs, at room temperature, lightly beaten
1 tbsp milk