Ripe banana provides deep, honeyed-sweetness in these little cakes, which works well with the bitterness in the double hit of dark chocolate from both the frosting and the ganache. Choose your favourite fruit and edible flowers to cut through the richness.
Make the sponges. Heat the oven to 180°C/160°C fan/350°F/Gas 4. Sift the flour, cocoa powder, baking powder and bicarbonate of soda into a large mixing bowl and stir to combine.
Whisk the bananas, olive oil, light brown soft sugar, almond milk and vanilla in a stand mixer fitted with the whisk, on medium speed for 1 minute, scraping down the inside of the bowl from time to time, until combined. Remove the bowl from the mixer, then gently fold in the flour mixture and white and dark chocolate with a metal spoon. Do not over mix.
Divide the mixture equally between the oiled cake tins. Bake the sponges on the middle shelves for 25–30 minutes, until they are risen with a cracked top, and a skewer inserted into the centres comes out clean. Leave to cool completely in the tins.
Make the frosting. While the cakes are baking, melt the dark chocolate in a heatproof bowl set over a pan of gently simmering water, stir until smooth and remove from the heat. Leave to cool for 10 minutes.
While the chocolate is cooling, beat the icing sugar, vegan spread and vanilla in a stand mixer fitted with the beater, on medium speed for 3–5 minutes, until pale and creamy. Fold in the melted chocolate. Spoon the frosting into the medium piping bag.
Make the ganache. Melt the chocolate with the almond milk in a heatproof bowl set over a pan of barely simmering water, stir until smooth and remove from the heat. Leave to cool for 10 minutes.
Assemble the cakes. Run a knife or spatula around the inside rim of each sponge to loosen, then turn them out. Slice each sponge horizontally in half. Pipe frosting over the bottom halves, then top with the other halves.
Place a heaped teaspoon of ganache on top of each sponge. With a clean teaspoon, make a small swirl pattern in the ganache and decorate with fruit, flowers and leaves.