In a jug, combine the milk with the vinegar and leave to one side to curdle. This is your vegan buttermilk.
Next, add the dates to a bowl and cover with hot water straight from a kettle, then leave them to soften while you carry out the next steps.
Preheat the oven to 180°C fan / 400°F, then grease 2 x 20cm (8”) cake tins with olive oil and line the base with baking paper.
Peel the bananas, add the flesh to a mixing bowl and mash with a fork until runny. Then add the maple syrup, vanilla extract, coconut oil and olive oil. Drain the dates well, then chop them until fine (so they resemble a paste). Then add them to the mixing bowl, along with the vegan buttermilk from earlier and give everything a good stir.
Next add the flour, cocoa powder, baking powder, bicarbonate of soda and a pinch of salt to the mixing bowl, and mix gently until fully combined. Divide the cake batter between the two cake tins and use a spatula to level out the mixture. Then use the stapula to create a slight dip in the middle of the batter in each tin, which will help to reduce the amount of rise.
Bake the cakes for 25-30 minutes or until a skewer comes out clean when inserted into the cake.
For the avocado frosting, add the flesh from the avocados to a food processor along with the maple syrup, cocoa powder and vanilla extract. Process until smooth, scraping down the sides as you go.
Once the cakes have finished baking, leave them to cool slightly in their tins. Then when they are cool enough to touch, remove them from their tins and peel off the baking paper from the base, then leave them to cool fully on a cooling rack.
Once fully cooled and you’re ready to serve, place one cake on a cake stand or serving dish, then spread a quarter of the avocado frosting over the top. Place the second cake on top and spread the remaining frosting around the top and sides of the cake. Then slice to serve.