Peel the green apples, remove the core and thinly slice. Place in a saucepan with 1 tsp of cinnamon and cover with water. Cover with lid, place over a hot stove and bring it to the boil. Reduce the heat, remove the lid and simmer for 10-15 minutes or until apples are soft and fragrant and the liquid has reduced a little. You do want the apples to be slightly watery. This is so the psyllium husk in the crumble can absorb this extra water giving both the apples and the crumble a great texture!
Meanwhile, to make the crumble: Mix the flour, oats, brown sugar, walnuts, remaining teaspoon of cinnamon, psyllium husk, chia seeds and nutmeg until well combined. Add the cubed butter and using your fingers rub the butter into the mixture until it resembles crumbs. Set aside.
Evenly place the apples along the bottom of an oven-proof ceramic dish or into the bottom of 8 individual serve ramekins. Top evenly with the crumble mixture. Bake for 20 or until the crumble is slightly golden.
Serve each portion of crumble with a generous dollop of yoghurt.