This simple sweet potato cake can also be an elegant addition to a breakfast or teatime when served with just a dusting of powdered sugar. Not overly sweet on its own but moist and rich tasting, it makes a beautiful and unusual occasion cake. My granny would make this wonderful sky-high cake for my birthday, and I loved it even with all of its grownup flavours. I make it now for my family, keeping the tradition and her memory alive.
Using a heavily peated whisky will add a subtle smokiness to the frosting; we usually have some on hand, and I sneak it from the cabinet for this recipe, but the cake really is just as lovely if the whisky is omitted. The maple syrup will take centre stage for a more familiar-flavoured frosting, beautifully complementing the earthy taste of the sweet potato. – R.K.
Ingredients
- 2 1/2 cups cake flour
- 1 tbsp baking powder
- 1 tbsp cinnamon
- 1 tsp nutmeg
- 1/4 tsp salt
- 1 1/2 cups light olive oil
- 1 1/2 cups brown sugar
- 4 eggs, yolks and whites separated
- 1 1/2 cups peeled, grated, raw sweet potato
- 1 tsp vanilla
Frosting
- 300 g cream cheese
- 1/2 cup butter
- 4 to 6 cups sifted icing sugar
- 2 tbsp maple syrup
- 1 tbsp peaty whisky (optional)
- 1 tsp sea salt
Method
- Preheat oven to 350°F.
- In large bowl, sift together cake flour, baking powder, cinnamon, nutmeg and 1/4 tsp salt.
- In separate large bowl, combine oil, brown sugar and egg yolks. In another clean bowl, beat egg whites until stiff peaks form.
- Add 1/2 cup hot water to oil mixture, alternating with flour mixture, making 2 additions of water and 2 of additions of flour mixture, ending with flour mixture.
- Mix in grated sweet potato, distributing evenly within cake batter.
- Fold in egg whites in 3 additions.* Do not overmix; keep as much volume as possible.
Divide cake batter evenly between 3 buttered and parchment-lined 8-inch (1.2 L) round cake pans. Butter the bottoms only; leaving the sides un-greased will allow the cake to rise higher, as the main leavening agent is the egg whites.
Bake until cakes have risen nicely and a skewer inserted in centre comes out clean, about 20 minutes. Let cool in pans on rack.
Frosting: Beat cream cheese with butter until light. Beat in icing sugar, gradually, until frosting becomes quite stiff. Beat in maple syrup, and whisky, if desired. Add salt to taste and beat until smooth and combined. When cakes are cool, remove from pans. Using sharp serrated knife, split each cake in half horizontally. Place first half on cake plate, cut side down. Spread 2 to 3 tbsp of the frosting over uncut side, leaving 1/2 inch of an edge free from frosting. Repeat with remaining layers. Use remaining frosting to decorate cake top and sides, if desired.
** The first addition of egg whites is to temper the batter. Use a whisk to mix a small portion of the beaten egg whites to lighten the batter before folding in the remaining egg whites in two additions, using a rubber spatula. Scrape the bottom of the bowl and gently lift the batter up and fold over the egg whites, gently repeating until the beaten egg whites and batter are mostly incorporated.
