Preheat the oven to 180°C/gas mark 4 and grease and line a 2-litre loaf tin. Sift the flour and baking powder together and set aside.
In a separate bowl, whisk the sugar, eggs, oil, almond milk and vanilla extract for 4-5 minutes until thick and glossy. Fold in the mashed avocado and dark chocolate until combined. Gently fold in the flour and baking powder. Scrape the mixture into the lined baking tin, then bake for 1 hour 5 minutes.
Test to see if it’s ready by inserting a skewer into the cake. If it comes out with just a few damp crumbs, it’s ready. If there is any sign of wet cake mixture, return the cake to the oven for 5 more minutes. Transfer the cake to a cake rack and leave in the tin until completely cool. Remove the cake from the tin and leave until cold, then slice and serve.