1. Heat oven to 190C/170C fan/gas.
2. Add 60g unsalted butter, mix granola using your fingertips to make a light breadcrumb texture. Do not overwork it or the crumble will become heavy.
3. Peel, core and cut 300g apples into small cubes.
4. Add 30g of sugar and a large spoon of butter in a medium saucepan and melt together over a medium heat. Cook for 3 mins until the mixture turns to a light caramel.
5. Stir in the apples and cook for 3 mins. Add a punnet of blackberries and a pinch of cinnamon, and cook for 3 mins more.
6. Cover, remove from the heat, then leave for 2-3 mins to continue cooking in the warmth of the pan.
7. To serve, spoon the warm fruit into an ovenproof gratin dish, top with the crumble mix, then reheat in the oven for 5-10 mins.