1. Line the base of a 23cm springform cake tin with baking parchment so you can remove the cake easily.
2. To make the base, put the almonds and cashew nuts into a food processor and whiz until they become coarse crumbs. Add the dates, vanilla extract and coconut oil, and blend until you have a breadcrumb-like texture. Transfer the mixture to the cake tin and use your hands to compact it really firmly into the base, ensuring an even spread.
3. To make the toffee layer, melt the coconut oil gently in a pan. Put it into a food processor with the rest of the ingredients for the toffee layer and blend until smooth and caramel-like. This can take up to 10 minutes - add more water if it's clumpy. Once ready, spread a really even layer of toffee on top of the base layer, doing your best to give it a smooth top. Put into the fridge for 20 minutes.
4. The base and toffee layers will keep like this for a week in the fridge, then all you have to do is to dress the cake before you serve. You can have the coconut cream ready in advance too.
5. Spoon the thick cream from both tins of coconut milk into a mixing bowl. Add 1 tablespoon of the clear coconut milk from one of the tins along with the vanilla extract, and whisk it all together with a fork or an electric whisk. The cream will keep for a week in the fridge, so you can also make this in advance.
6. To assemble the cake, remove the springform tin, carefully peeling away the parchment lining, and transfer the cake to a flat plate without a dip in it.
7. Slice the bananas into little 'coins' and put a layer of these on top of the toffee layer. Spoon the coconut cream on top, then, using the fine side of a grater, grate the chocolate on top.
8. Refrigerate before serving, as the coconut crean with go a bit runny at room temperature if left out for too long. Store the cake in the fridge - if there's any left over!