500g/1lb 2oz blackberries, frozen or fresh
1 lemon, juice and zest only
240g/9oz plain flour, plus extra for flouring
50²µ/1¾´Ç³ú caster sugar
½ tsp ground cinnamon
1 tbsp cornflour
60g/2¼ oz ground almonds
140g/5oz cold butter, diced
1 free-range egg yolk, beaten
good-quality vanilla ice cream