Korean Sweet Potato Cake
Craving something cozy and unique? Korean Sweet Potato Cake (Goguma Cake) is layered with fluffy genoise, creamy sweet potato filling, and light whipped cream. Its natural sweetness and velvety texture make it a comforting dessert everyone will love!
Servings: 16
Ingredients
MAIN
- 450 g sweet potatoes (Hawaiian or Okinawan), peeled and sliced into 2.5 cm (1-inch) pieces
- 1 tall vanilla sponge cake (around 4.5cm or higher), 2 shorter vanilla sponge cakes (each about 3cm tall), or an equivalent amount of Genoise sponge
SWEET POTATO FILLING
- 1/3 cup milk , full cream
- 2 Tbsp white sugar
- 1 Tbsp sweetened condensed milk
- 30 g unsalted butter (1 ounce)
- 1/4 cup stabilized whipped cream (see below for how to make it)
VANILLA CAKE SYRUP
- 1/4 cup water
- 2 Tbsp white sugar (granulated)
- 1/2 tsp vanilla bean paste
Stabilized Whipped Cream
- 2 cup thickened cream
- 1 cup mascarpone (e.g., La Casa Del Formaggio Mascarpone 250g from Woolworths, Montefiore Mascarpone 250g from Coles, or BelGioioso Mascarpone 8 ounces in the US)
- 1/2 cup icing sugar (powdered sugar)
Instructions
- Steam the sweet potatoes over medium heat for 25-30 minutes, or until they are fully cooked. To check the doneness, gently poke them with a chopstick—they should be soft and easily pierced.
- In a medium-sized pot, combine the milk, sugar, sweetened condensed milk, and unsalted butter. Cook over low heat, stirring frequently, until the sugar is completely dissolved. Add the steamed sweet potatoes to the pot and mash thoroughly using a potato masher until smooth. Transfer the mashed mixture to a bowl and let it cool completely.
- Prepare the vanilla cake syrup. Mix water, sugar, and vanilla bean paste in a small bowl. Microwave the mixture for 30 seconds and stir until the sugar dissolves completely. Set aside.
- Prepare cake base layers. To create three 1.5cm cake base layers, start by assessing your cake:- For a single tall cake (around 4.5cm or higher): Slice it horizontally into three equal layers, each approximately 1.5cm thick. - For two shorter cakes (each about 3cm tall): Slice both cakes horizontally in half. This will give you four layers in total. Choose the three most even layers to assemble your cake base.Set the extra layer aside— it’s optional but can be grated for decoration later.
- Generously brush each cake layer with vanilla syrup to enhance the flavor and keep the sponge moist. You can do this during step 9 if it suits your workflow, but I prefer doing it now to avoid forgetting later.
- This step is completely optional, but if you’d like to use cake crumbs for decoration, grab any leftover cake layers or sponge scraps and trim away the brown edges for a consistent, even-colored crumb. Once trimmed, grate the sponge and then pass it through a sieve to create fine, fluffy pieces. These delicate crumbs make a beautiful decorative topping, adding a soft and polished touch to your cake.
- Start by combining thickened cream, icing sugar, and mascarpone in a chilled mixing bowl. Whip the mixture until stiff peaks form. For best results, keep the whipped cream extra cold by placing the mixing bowl inside a larger bowl filled with ice while proceeding with the next steps.
- Gently fold 1/4 cup of whipped cream into the sweet potato mixture (from step 2) until smooth and creamy. Continue mixing until fully combined and velvety.
- To assemble the cake, transfer the whipped cream and sweet potato mixtures into separate piping bags. Place the first sponge cake layer on a cake turntable. Pipe and spread an even layer of whipped cream over the top. Add the second sponge cake layer, then pipe and spread a generous layer of sweet potato filling. Finally, place the third sponge cake layer on top and cover the entire cake with a thick, even coat of whipped cream. Smooth the whipped cream around the sides for a polished finish.Tip: Humidity can affect the stability of whipped cream, especially when piping. If the cream appears runny or struggles to stick to the sides, chill both the cake and whipped cream briefly before continuing. I also recommend turning on the air conditioning to keep the environment cool and reduce the impact of humidity. This will help stabilize the cream and ensure a smoother finish.
- Decorate the cake as creatively as you like! For instance, sprinkle the sponge cake crumbs prepared in step 6 over the top. Add a playful touch with sweet potato chips and pieces of leftover boiled sweet potato. Once decorated, refrigerate the cake for at least an hour to let the cream set beautifully. When ready, slice and enjoy!
Notes
- 1 Tbsp = 15 ml, 1 cup = 250ml