Cupcakes: Preheat oven to 180 Celsius. Prepare the apples. Peel, core and chop them into cubes. Put into a medium pot half filled with water and boil for 7 minutes, until soft. Once the apples are soft, drain them well and set aside. Cream together the butter and sugar. Whisk in eggs. Sift in all the dry ingredients. Mix until incorporated. Fold in the apple. Fill a cupcake pan with cupcake wrappers and scoop the batter evenly in. Bake for 15-20 minutes.

Crumble: Preheat oven to 180 Celsius. Using your fingers, rub the butter into the flour, sugar, and cinnamon, until the mixture resembles coarse breadcrumbs. Line a baking tray. Spread the crumble evenly over the tray and bake until golden, about 5-10 minutes.

Icing: Cream together the butter, brown sugar, vanilla essence, and cinnamon until creamy and combined. Mix in the icing sugar. Once incorporated, mix in the milk until the icing is soft, but can hold it's shape.

Assembling: Spread a layer of icing on top of a cupcake using a knife. Dip the cupcake into a bowl filled with the crumble topping so it sticks.