Line 8 x 8 inch or 11 x 7-inch pan with parchment paper. Preheat oven to 350˚F.
In a large bowl mix together the flours, oats, sugar, spices, salt and chopped walnuts. Rub or cut in the non-dairy butter until the mixture resembles wet sand.
Reserve 1 cup of mixture to use as a crumble topping later and pour rest into lined pan. Press down evenly and firmly to create the bottom crust. Bake for 20 minutes in the centre of the oven, until the edges start to become golden.
While the crust is baking, prepare the apple filling. Place the apples, sugar, butter, cinnamon and lemon juice in a heavy based pan. Cook over a gently heat until the apples have cooked down and are soft. The mixture should be like a thick puree with some pieces of apple left intact.
Once the bottom crust has finished cooking, spread the apple filling over it evenly. Sprinkle the reserved crumble topping over the apple filling evenly. Return to oven and bake for 40 minutes.
While the crumble bars are cooking prepare the caramel drizzle. Add the maple syrup, coconut butter, salt and vanilla extract to a small heavy based pan. Warm gently (do not allow to burn) until everything melds together to become a smooth, caramel sauce.
Allow to cool in the pan for about 45 minutes. Remove from the pan and transfer to a wire rack to cool fully. Once cool cut into bars and drizzle with the caramel.