Place cashews in a bowl of boiling water and to leave to soak for 20 minutes.
Line your tray or cake tin with baking paper.
In a processor blend 1 cup of the hazelnuts, almond meal, cacao powder and 1 teaspoon of the vanilla essence until the mixture resembles coarse crumbs. Add the pre blended buckwheat groats, rice malt syrup and 2 tablespoons of the coconut oil until combined. Once combined press the mixture firmly and evenly into the tin using a spatula. Pop this in the freezer while you do the rest.
Drain the cashew nuts and blend with the remaining coconut oil, chocolate hazelnut butter, maple syrup, coconut cream, remaining vanilla essence, hazelnut flavour and salt until completely smooth. Pour half of this mixture onto the base and smooth the top out, put in the freezer.
Finely chop and toast in a fry pan 2/3 cup of hazelnuts. Let these cool and sprinkle over the filling. Pour over the remaining cashew mixture and smooth the top. Cover with a bees wax wrap and freeze for 3 hours.
Blend the ganache ingredients together in a food processor and pour over the tart, refrigerate for about 20 minutes. Coarsely chop the remaining hazelnuts and sprinkle over the top.