Purple Magic Cake

Here’s the thing, I had some Purple Sweet Potato (Ube) and Soy Milk (made by me) at home. I wanted to use them and make something tasty for tea time. I started cooking Purple Sweet Potato into purée and then I came up with the image of soft purple cream oozing out of soft sponge when you put a fork into it … That was the moment I decided to make a ‘Purple Magic Cake with Soy Milk’.

You might be wondering ‘What is a Magic Cake?’ OK, I explain. A Magic Cake is a custardy moist spongy cake made with whipped Egg and quite large quantities of liquid. When you bake it comes out in three layers with a very light spongy top layer, soft and moist middle layer and creamy custardy base layer.

I have put a recipe of a type of Magic Cake almost a year ago on this Blog. That was ‘Sake Soufflé Quiche with Figs & Pine Nuts’ which I received the Second Award in the Sake Cooking Competition with that recipe last year.

My experiment went on ….

Purple Magic Cake with Sweet Potato & Soy Milk



  • 2 Large Eggs
  • 60g of Unsalted Butter
  • 70-80g of Granulated Sugar (divide into 45-55g and 25g)
  • 150ml of Purple Sweet Potato Purée
  • 100ml of Soy Milk (or Cow Milk)
  • 50g of Plain Flour
  • 1 Tsp of Vanilla Extract

(Tools to prepare)

  • Round Cake Tin in 15cm diameter
  • Baking Tray deeper than 3cm


Preheat the oven at 150℃.

Divide Yolk and Egg White into separate bowls. Add 45-55g of Sugar into Yolk and mix well until it becomes lightly creamy colour and fluffy.

Melt Butter and cool it down to room temperature. Add the cooled Butter and Vanilla Extract into Yolk mixture. Add in Plain Flour and mix thoroughly with a whisk.

Add in half of Purple Sweet Potato Purée. Mix well to incorporate the mixture. Add in the rest of the Purée and Soy Milk. The texture becomes very liquidy but do not worry.

Whisk Egg White with 25g of sugar in another clean bowl until it forms stiff peaks. Add the 1/3 of whipped Egg White into the Yolk mixture and combine well. Add in the rest of whipped Egg White into the mixture but this time mix very lightly and leave some blobs of Egg White floating around.

Pour the mixture into a cake tin with baking sheet in. Cover the bottom and side part of the tin with a sheet of aluminium foil if you use a tin that the base comes off. Place the tin on the baking tray and pour hot water onto the tray outside of the cake tin up to about 2cm in depth. Place the baking tray into the preheated oven and bake for 45 minutes.


It turned out to be slightly on the softer side this time and the bottom part was quite runny. This made it very hard to take a good photo of this cake but I received a great compliment from someone who had a sample that “It was the best cake I had ever tasted!”

It came out with plenty of Sweet Potato flavoured custard so it did not need any additional sauce or cream to go with it. You can adjust the amount of sugar according to how sweet the Purple Sweet Potato is and also to your taste.


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