This little vegan chocolate cake is much more than just a dessert; it is utter indulgence on a plate, with an unexpected ingredient, the humble sweet potato. Combining the richness of dark chocolate with the subtle warmth of rum, the cake is sheer nostalgia, which honestly makes it perfect for cosy evenings and small gatherings. And if you love the flavour of rum in your cakes as much as I do, feel free to add a tiny splash to the cake itself, it will pair perfectly with the cinnamon and cocoa powder.
My tips for success.
Sweet potato can be baked, boiled and drained well, or even steamed - as long as it is mashed well and not watery, it will be perfect. Its natural sweetness pairs really well with the chocolate flavour, and the texture is simply perfectly fudgy.
If your filling seems a bit too soft, which can happen due to differences in vegan cream or how dry the sweet potatoes were, feel free to add a bit more of unsweetened cocoa powder or even two teaspoons of whipped cream stabiliser (modified starch, essentially). Both will work well.
The chocolate I used is the 75% one, as that is my absolute favourite, but feel free to use an even darker, more intense chocolate bar, if you prefer that. Because of the sugar content in the cake, it will be fine to go even up to 90% of cocoa solids for the frosting.
Ingredients
For the sweet potato chocolate cake
90 grams plain flour, sifted
1 ¼ teaspoons baking powder
½ teaspoon ground cinnamon
¼ teaspoon salt
120 grams sweet potato, cooked and mashed
130 grams light brown sugar
50 millilitres vegetable oil
1 heaping teaspoon vanilla bean paste
120 millilitres boiling water
20 grams unsweetened cocoa powder
For the sweet potato chocolate rum filling
80 grams sweet potato, cooked and mashed
80 grams dark chocolate (75%)
20 millilitres dark rum
20 grams icing sugar, sifted
20 grams unsweetened cocoa powder
120 millilitres vegan double cream
½ teaspoon vanilla bean paste
Preparation
Start by making the chocolate fudge cake. Let the oven preheat to 180°C and line a small (16 cm) round cake tin with baking parchment. Mix the cocoa powder and sugar with the boiling water and let it cool down slightly. In a separate bowl, whisk together the mashed sweet potatoes, oil, and vanilla until smooth. Add in the somewhat cooled bloomed cocoa powder and the sugar, and mix well.
Finally, sift in the dry ingredients and fold them through gently, making sure not to overmix the batter. Pour it into the prepared cake tin, level the top, and bake immediately, in a nicely preheated oven, at 180°C, for about 20-25 minutes. Just like any cake or brownies, check it with a toothpick to make sure it does not dry out. Take it out of the oven and let it cool down completely in the tin.
Once the cake is cool, proceed to make the filling. Melt the dark chocolate over low heat or in the microwave, and let it cool down. Place the mashed sweet potatoes in a medium bowl, add in the rum, icing sugar, and the cocoa powder, and mix well. Add in the cooled chocolate, and fold it through. Take a large bowl and whip the chilled vegan double cream and vanilla until soft peaks form.
Add in the chocolate batter and keep mixing on the medium setting until very stiff peaks form. Spread the frosting over the cooled cake, and place the whole tin in the refrigerator for at least 8 hours. Once ready to serve, remove from the cake tin, top with chocolate shavings or some unsweetened cocoa powder, and serve with freshly brewed coffee. Yields 6 servings.
