Peel the apples and remove the core, cutting them into bite–sized pieces.
Put the apples into a saucepan with 2 tbsp of filtered water. Cook gently on a medium heat for about 8–10 minutes until soft but still retaining bite.
Transfer to a baking dish.
Melt the coconut oil in a saucepan. Add the maple syrup, cinnamon, cardamom and ginger. Pour this over the oat/nut mixture and stir well until all the dry ingredients are coated with the coconut oil mix.
Distribute the topping mixture over the apples.
Sprinkle the walnuts evenly on top of the crumble and bake until golden (20–30 minutes).