Heat the oven to 200C, 180C Fan, 400F
500 g apples
Fill a bowl with water, peel the apples and put into the water to stop them browning. Quarter, core and slice the apples and place in the ovenproof dish.
150 g blackberries, 200 g golden caster sugar, 1/2 teaspoon cinnamon, 1 tbsp cornflour
Add the blackberries to the apples and sprinkle over 50g (2oz) of the sugar, as well as the cinnamon and cornflour.
Gently stir everything together to mix the apples and blackberries with the dry ingredients.
150 g self-raising flour, 50 g chilled butter, cubed, 200 g golden caster sugar
Put the flour in a bowl or food processor, add the butter and the remaining 150g (5oz) sugar, and cut with a knife or whizz until it forms crumbs.
100 ml buttermilk
Add the buttermilk and blend until a squidgy dough forms.
Scatter clumps of the dough over the fruit - don't cover completely.
1 tbsp demerara sugar
Sprinkle with the demerara sugar and bake for 40 minutes, or until the fruit is tender and the cobbler golden.