200g/9oz fresh blueberries
1 lemon, zest only
handful of large mint leaves, picked from their stems
250g/7oz plain flour
100驳/3陆辞锄 caster sugar
2 tbsp caster sugar, plus a little extra for cooking
15驳/陆辞锄 icing sugar
1 tbsp icing sugar, plus more for sprinkling
pinch salt
knob of butter
1 free-range egg
1 free-range egg white
2 tbsp sour cream
100ml/3陆fl oz sour cream or cr猫me fraiche