I baulked at eating a marshmallow-topped sweet potato casserole with the turkey an American friend served at her Thanksgiving dinner, but the combination did set off a light bulb in my head. Inevitably, my mind turned to cakes, and here is the result. I've added spices to temper this cake's sweetness, and topped it with an icing that has the sticky chewiness of marshmallow. This cake benefits from a bit of time, so make it a day or two before serving, and ice it on the day.
320g plain flour
1¼ tsp baking soda
1 tsp cinnamon
1 tsp ginger powder
¼ tsp ground cloves
½ tsp salt
150g light brown sugar
150g castor sugar
1 tsp orange zest
90ml vegetable oil
3 large eggs
180g mashed sweet potato, cooled
1 tsp lemon juice
1 tsp vanilla
80g pecans, toasted and roughly chopped
For the icing
2 large egg whites (60g)
70g castor sugar
3 tbsp maple syrup
½ tsp vanilla extract
1. Preheat oven to 195C (175C fan-forced). Grease and line the bottom and sides of a 20cm round cake tin with baking paper.
2. Place the flour, cornflour, baking soda, cinnamon, ginger, cloves and salt in a medium bowl. Whisk to combine and set aside.
3. Combine butter, sugars and orange zest in the bowl of a cake mixer and beat with the paddle attachment on medium speed for about 1 minute, then add the vegetable oil. Continue to beat on medium speed until the mixture lightens, both in colour and texture (about 1 minute). Add the eggs, one at a time, then the mashed sweet potato, and beat on low speed for a few seconds until just incorporated.
4. Combine the milk and lemon juice, then, beginning with the dry ingredients, add alternately to the creaming mix on low speed. Don't beat it too much, just enough to incorporate the ingredients. Remove the bowl from the cake mixer and fold in the vanilla and pecans.
5. Scrape the batter into the prepared cake tin and bake for 45 to 50 minutes, or until a skewer inserted into the centre of the cake comes out clean.
6. Place the tin on a wire rack for around 30 minutes, then turn the cake out onto the rack to cool completely before icing. Better still, wrap in cling film and refrigerate for up to 2 days before topping with the icing and serving.
7. To make the icing, fill a medium saucepan with enough water to rise a quarter of the way up the sides, then bring to a boil. Meanwhile, place all the ingredients for the icing in the bowl of a cake mixer and whisk by hand to combine. Reduce the heat under the saucepan to a simmer, then set the bowl over the pan, making sure the water does not touch the base of the bowl. Whisk continuously by hand until the mixture is warm and frothy and the sugar has melted (about 3 minutes), then transfer to the cake mixer with the whisk attachment in place. Whisk on high speed until the mixture is cool, stiff and glossy (about 5 minutes).
8. Spread the top of the cake with the icing, then form swirls and peaks with the back of a spoon. If you have a kitchen blowtorch, use it to scorch the marshmallowy icing all over, moving the torch around so that it doesn't catch and burn. Once iced, the cake will keep for up to 2 days.
Find more of Helen Goh's recipes in the Good Food Favourite Recipes cookbook.