Preheat your oven to 160°C

Chop the apples into 2-3cm pieces and place in a medium saucepan over medium-low heat. Add the brown sugar and cinnamon and stir to combine.

Allow to cook, stirring regularly, for 5-10 minutes until the apples have softened slightly on the outside but are still crisp throughout.

In a small bowl, mix the corn flour with the water to make a slurry and add this to the apples, stirring well. This will thicken the juices in the saucepan so that it coats the apples. Transfer to a 24 x 18cm baking dish and spread into an even layer. Set aside.

To make the crumble topping, combine the remaining ingredients except for the muesli in a large bowl. Rub the butter into the dry ingredients with your fingers until it starts to clump, then add the muesli.

Combine the muesli with the flour and butter mixture until it is mixed through to make a rough crumb. There should be some large clumps as well as some looser crumbs.

Tip the crumble mixture into the baking dish, spreading it in an even layer over the apples. Transfer to the oven and bake for 40-45 minutes.

Allow to cool slightly, then serve hot with cream or ice cream.