Preheat oven to 180°C fan (200C/gas 6) and prepare 2 x 20cm cake tins with baking parchment.
Make the cake batter by combining flour, cocoa powder, baking powder, vanilla extract, maple syrup, and plant-based milk in a food processor or bowl.
Pour half the batter into each tin and bake for 25 minutes.
Let the cakes cool in the tins, then transfer to a cooling rack for at least 30 minutes.
For the icing, blend cocoa powder, icing sugar, dairy-free butter, vanilla extract, and plant-based milk until smooth.
Layer the first cake on a plate, spread a third of the icing on top, then place the second cake on top.
Cover the entire cake with the remaining icing and refrigerate for 1 hour before serving.
