Japanese Sweet Potato Cake

Japanese Sweet Potato Cake
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My original intent was to recreate an Ube (purple potato) cake, typically found in Filipino bakeries. It wasen’t until I started prepping that I realized that I did not have purple potatoes (purple skin and purple flesh). I had Japanese Sweet Potatos (purple skin and pale yellow flesh)! So, by accident, I ended up cooking a slightly different cake altogether. And since I got the wrong tubular, changing the frosting also seemed…appropriate. New cake, new frosting combination, still delicious and still pretty.

Japanese Sweet Potato Cake

Japanese Sweet Potato Cake

Inspired by the skin of vibrant purple potatoes, this lightly sweetened cake with Japanese Sweet Potatoes is a winner!
Course Dessert


  • 2 x 8" round cake pans
  • balloon whisk
  • rubber spatula
  • Medium bowl
  • 2 x Large bowls
  • Electric mixer


  • 2 ½ cups cake or self raising flour
  • 3 teaspoons baking powder or 1 teaspoon if using self raising powder
  • ¼ teaspoon salt
  • 1 cup Japanese Sweet Potato peeled, cooked (I microwaved 1.5” slices for ~5 minutes) and finely grated
  • 1/3 cup corn syrup
  • ½ cup vegetable oil
  • ¾ cup milk
  • 1 teaspoon vanilla extract
  • 7 egg yolks
  • 7 egg whites
  • 1 teaspoon cream of tartar
  • ½ cup white sugar

Purple Frosting

  • 3 oz Purple Grape Jello 85 g, 1 box
  • ½ cup white sugar
  • 1 egg white
  • 1 teaspoon vanilla extract
  • ½ cup boiling water



  • Preheat oven to 325F.
  • Line 2 8” cake pans with parchment circles.
  • In a small bowl, mix cake flour, baking powder and salt together and set aside.
  • In a large bowl, add grated Japanese Sweet Potato, corn syrup, vegetable oil, milk, vanilla and egg yolks. Use a balloon whisk, mix these wet ingredients together. Set aside.
  • In a large bowl, beat egg whites and cream of tartar to soft peaks. Add sugar and whip to stiff peaks about 5-7 minutes.
  • To the Japanese Sweet Potato mixture, set aside the balloon whisk and use a rubber spatula to fold in the dry flour ingredients.
  • Add ½ of the egg whites to the Japanese Sweet Potato mixture and fold in.
  • Add remaining egg whites to Japanese Sweet Potato mixture and fold in.
  • Pour cake batter into cake pans. Bake for 35-40 minutes or until a toothpick in the center of the cake comes out clean.
  • Cool cake layers in pan until ready to frost.


  • Combine jello, sugar, egg white and vanilla extract in a bowl.
  • Using an electric mixer, whip ingredients until well mixed.
  • Slowly add ½ cup of boiling water and whip 5-10 minutes until frosting is thick, frothy and stiff peaks.

Cake and Frosting Assembly

  • Use a butter knife to generously separate cake along the edge of the pan.
  • Set one cake layer onto serving plate
  • Spread layer of frosting across the top.
  • Add additional cake layer on top of the frosting.
  • Generously spread frosting along sides of the cake and the top.
Keyword cake, eggs, gelatin, Genoise, Japanese, jello, sponge cake, sweet potato, yam

Thanks to Leelalicious blog for the base Ube cake that I converted to my own taste.

Thanks to Happier than a Pig in Mud blog for the base of the Jello frosting recipe.

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