Korean Sweet Potato Cake
Korean sweet potato cake is my favourite type of cake, so I made it and it turned out fabulous! Korean sweet potato cake has a layer of sponge cake at the bottom and a creamy sweet potato filling. For the covering, you spread on some whipped cream and sprinkle the entire cake with ground sponge cake crumbs.
Except, I'll be honest. The filling turned out a little too creamy. It should have been firmer.
Well, I've learned something from that: That the quality of your ingredients is very very important during baking. I made this cake with another type of sweet potato than the one directed in the recipe... So I got a runny filling.
And, I boiled the sweet potatoes for too long in water. I should have baked them or something to reduce moisture. Here is my improved, fixed recipe below. The only thing I changed is the method of preparing the sweet potato.
Korean Sweet Potato Cake (Makes one 8-inch cake)
Ingredients
FOR THE SPONGE CAKE
-4 1/2 eggs
-150g white granulated sugar
-135g all-purpose flour (or cake flour)
-30g melted butter
FOR THE CUSTARD CREAM
-2 1/2 egg yolks
-75g white granulated sugar
-40g corn starch
-375ml milk
-13g butter
FOR THE SWEET POTATO CREAM
-750g sweet potato
-40g room-temp. butter
-55g honey
-125ml heavy cream
DECORATION
-190ml heavy cream
-almonds
Instructions
1. Line a 8-inch spring-form pan with parchment paper.
2. Pour hot water into a big basin. Place a smaller bowl on top of it. Fill the smaller bowl with the four and a half eggs.
3. Beat the eggs with a whisk until pale and foamy.
4. Add the sugar little by little, dividing it into three additions. Beat after each addition, by tilting your bowl and whisking in a vertically circular motion. Do so until the mixture is thick. When you lift your whisk, a trail should be left behind, like honey.
Preheat your oven at this point to 180 degrees Celsius.
5. Sift in the flour and fold it in quickly with a spatula. If you mix too much, the delicate air bubbles inside the mixture (which you want) will disappear! Only mix until well-incorporated.
6. Scoop out a spatuful of the batter and plop it into the melted butter. Whisk with a fork and pour it back into the batter. Fold with a spatula just until fully incorporated.
7. Pour the batter into your prepared pan. Put it in the oven and bake for about 30 minutes, or until a toothpick inserted into the center comes out clean.
8. Let it cool a little before removing from pan. Then cool completely on a rack.
9. Slice out a 1-cm thick layer from the sponge cake. For the rest of the sponge cake, slice out any brown parts.
10. Place the 1cm thick layer of sponge cake on a plate. Wrap a cake collar around it. In a food processor, grind the rest of the sponge cake (except brown parts) into bread crumbs.
11. To make the custard dream, add egg yolks to a large bowl and whisk lightly. Add the sugar and whisk until pale and yellower in colour. Sift in the corn starch and whisk lightly.
12. In a little saucepan, heat the milk over low heat until the edges begin to simmer.
13. Add that milk in a slow, thin stream into the custard mixture from step 11. Whisk rapidly while doing so.
14. Pour the custard mixture into a small saucepan and heat at medium heat. Do so for about 2 minutes, whisking rapidly until the custard boils over to the center. The finished custard should be thick enough to coat the back of a spoon.
15. Turn off the heat and stir in the butter until fully melted and incorporated.
16. Put the custard on a plate. Cover with plastic wrap so that the film touches the custard. Refrigerate to cool.
17. Slice the sweet potatoes in half lengthwise and bake in the oven at 250 degrees C. Do so until they are cooked. Check the doness by inserting a toothpick. Let the sweet potatoes cool enough to be able to remove their skins and flaws.
18. Place the sweet potatoes into a large bowl and mash them until smooth. Add the butter, honey, and heavy cream and whisk until smooth and fully incorporated.
19. Get the custard cream out from the fridge and whisk a little bit to smoothen it up. Then add the sweet potato mixture to the custard cream and whisk until smooth. If the whisk is too weak, use a wooden spoon to stir the thick cream until fully incorporated.
20. Fill the cake collar (with sponge cake layer at bottom) with the finished cream filling. Smooth the top out with a scraper. Refrigerate for 1 hour.
21. In a bowl, whisk the heavy cream until stiff peaks form. (When you whip up heavy cream for cakes, overwhip them a little)
22. Take the cake out of the fridge and unwrap the cake collar. Then with an offset spatula, spread the whipped cream all over the sides and top, in a thin layer.
23. For the fun part, sprinkle the cake crumbs all over the cake. (You might need to gently press them on) The leftover crumbs are delicious to just scoop and eat!
24. Garnish with almonds if desired. Enjoy!!!
Recipe adapted from a Korean cookbook named 진짜 기본 베이킹 책 by super recipes. http://www.super-recipe.co.kr/etc_06/etc_s4_01.php?inc=view&idx=130&tbname=notice