Soak the cashews in warm water for 15 minutes
Meanwhile, put the chocolate in a bowl in a double boiler and melt
Once the 15 minutes are up, drain the cashews and add to a high speed blender
Blend till smooth - it will take some time and you will need to scrape the sides of the blender
Add the melted chocolate, milk and avocado and whizz till it is incorporated and smooth
Pour the mixture into a little bowl or a small spring form pan
Keep in the freezer for around 10 mins
Take out and drizzle the remaining melted chocolate on top of the cake
Put it back in the freezer and leave it for around 1/2 hour
Take it out and remove from the pan. Store in the fridge