200g/9oz fresh blueberries
1 lemon, zest only
handful of large mint leaves, picked from their stems
250g/7oz plain flour
100²µ/3½´Ç³ú caster sugar
2 tbsp caster sugar, plus a little extra for cooking
15²µ/½´Ç³ú 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/3½fl oz sour cream or crème fraiche