1 Line a 15cm round loose bottomed cake tin with cling film.
2 Soak the dates and almonds in boiling water for 20 to 30 minutes. Meanwhile, melt the block of cacao in a heat-proof bowl over a pan of simmering water.
3 Drain the dates and almonds and blitz to a paste in a food processor. Add the melted cacao and cocoa powder, and blitz again until the paste is smooth and fairly stiff – you may need to do this in 2 batches. Transfer the mixture to a bowl and place in the fridge to cool.
4 Meanwhile, make the icing by peeling and removing the stone of the avocados. Place the avocado flesh in a food processor with the orange juice and zest, honey and cocoa powder and blitz until smooth. Transfer the mixture to a bowl and place in the fridge.
5 Once the mixture has cooled you can start to construct the cake. Place half the cake mixture in the tin and lightly dust with cocoa powder, then add a thin layer of icing and a sprinkling of the nuts. Add the remaining cake mixture, smooth over and place the cake in the fridge for 40 minutes to set.
6 Remove from the tin and spread the remaining icing over the sides of the cake, then scatter with the remaining nuts.