Peel and chop your apples into 2cm cubes
Put them in a saucepan along with the light brown sugar, cinnamon, and salted butter
Cook on medium-high heat until slightly softened (not too soft!)
Spread the apples out into an oven proof dish
In a separate bowl, add in the cold cubed butter, caster sugar, light brown sugar, and plain flour
Rub together with your finger tips for about 5 minutes until it clumps together like crumble!
Sprinkle the crumble over the top of your apples and then bake in the oven at 180°C fan for 25 minutes
Serve with warm custard
