"Chocolate mud cake is always a winner! In this recipe, using potatoes instead of flour gives the cake a rich, luxurious consistency. It is not traditional but, in the new Nordic style, makes great use of the region’s most beloved vegetable. Fans of dark chocolate will particularly enjoy this cake because it’s loaded with bitter cocoa — make sure you use top quality cocoa powder though, as there’s no disguising an inferior product. The potatoes will help the cake keep moist for at least a day or two after baking." — Simon Bajada, author of The New Nordic: Recipes from a Scandinavian Kitchen
Boil the potatoes (in their skins) in a large saucepan of water for 10–15 minutes, until soft. Drain the potatoes and then carefully peel away and discard the skins and mash the flesh until very smooth. You can also pass the cooked potatoes through a ricer. Chill in the refrigerator until cool.
Preheat the oven to 300 degrees F.
Whisk the eggs, superfine sugar, baking powder, and butter in a large bowl for about 5 minutes, until pale and fluffy. Add the cocoa powder and whisk for 1 minute more.
Add the cooled potatoes and combine only until the white potato colour is absorbed by the brown. If you over-mix, the starch from the potatoes will make the batter gluey and affect the texture of the cake.
Grease an 8-inch round cake pan with butter and sprinkle the breadcrumbs on the base and along the sides of the pan. Spoon the batter into the pan. It will be thicker than a normal cake batter, so use a spatula to smooth over the surface. Bake the cake in the oven for 40 minutes. It will resemble a classic mud cake. Allow the cake to cool in the tin for 10 minutes, before transferring it to a serving plate.
Sprinkle the cake with confectioners sugar and serve it with whipped cream.