375g/13oz frozen blackberries
1 tbsp caster sugar
1 tsp cornflour
140g/5oz plain flour
85g/3oz unsalted butter, cubed and chilled, plus extra for the dish
60g/2½oz soft light brown sugar
double cream, to serve
Heat oven to 180C/160C fan/ gas 4. Put the blackberries in a bowl with the caster sugar and cornflour, and toss to mix. Tumble the berries into a buttered baking dish and set aside for 15-20 mins.
Put the plain flour and butter in a large bowl and use the tips of your fingers to rub the butter into the flour until the mixture resembles coarse breadcrumbs. Stir in the brown sugar, then sprinkle the mixture evenly over the berries and bake for 45-50 mins, until the top is golden brown. Let the crumble cool slightly before serving with cream.