about 200g/7oz blueberries
1 lemon, zest only (use the juice in the icing, see below)
2 tbsp lemon juice
about 150g/5½oz raspberries
about 150g/5½oz medium-sized strawberries, hulled and sliced
2 tsp baking powder
250g/9oz golden caster sugar
375g/13oz icing sugar
300g/10½oz self-raising flour
2 tsp vanilla extract
150g/5½oz butter, well softened
125g/4½oz butter, well softened
4 free-range eggs
1 tbsp milk
200g/7oz full-fat soured cream