Place in a saucepan with the sugar, cinnamon and 3 tbsp water, cover and place over a low heat for 5-10 mins, allowng it to cook until the apples are beginning to soften.
Preheat the oven to 180C/Gas 4.
Put the flour (or a mixture of flour and ground almonds) in a bowl, add the butter, cut into small chunks, and rub it in until the mixture resembles fine breadcrumbs.
Add 125g demerara sugar and stir well.
Put the apples in an ovenproof dish, cover with the crumble mix, sprinkle over 1 tbsp rolled oats and 1 tbsp demerara sugar and bake for 30-40 mins until golden.
Remove and leave to rest for 5-10 mins, then serve warm with vanilla ice cream or fresh whipped cream.
Recipe by appetite magazine at https://www.appetitemag.co.uk/apple-crumble/