There was an error in this gadget

Monday, 24 April 2017

Purple Sweet Potato Butter Cake 紫薯牛油蛋糕

I baked this purple sweet potato butter cake as I have some steamed purple sweet potato leftover after baking my Purple sweet potato bread. The purple sweet potato, which only present in small quantity in this cake recipe, was not strong enough to affect the aroma of the butter cake. It just helped to make some nice contours in the moist and velvety cake :)

Pan size: One 26Lx10Wx7H cm loaf pan


Ingredients in room temperature

110g unsalted butter, softened 无盐牛油,软化
105g fine sugar 细糖

3 eggs 鸡蛋

110g top/cake flour 低筋面粉
15g milk powder 牛奶粉
1/2 tsp baking powder 泡打粉

20ml lemon juice 柠檬汁
15g honey 蜂蜜
1/2 tsp lemon zest 柠檬皮削
1/2 tsp vanilla esscence 香草精

40~50g steamed purple sweet potato paste 


1. Coat the loaf pan with butter, followed by dusting some top flour over it. Set aside.

2. Mash the steamed sweet potato into paste. Cover and set aside.

3. Collect 20ml of lemon juice, and 1/2 tsp of lemon zest from a lemon. 

Pour lemon juice, honey, lemon zest, and vanilla essence, in a small bowl.  Set aside.

4. Cream softened butter and fine sugar, till pale and fluffy using a hand whisk. Set aside.

5. Beat eggs till frothy.

Add beaten egg into the butter cream from (4) gradually.  Start adding the next batch of beaten egg after the previous batch has been well Incorporated with the butter cream.

6. Mix top/cake flour, milk powder and baking powder in a separate mixing bowl before sifting into the butter cream mixture.

7. Blend in the lemon-honey mixture from (3).

Give the batter a more thorough mix using a spatula.

8. Take about 1/4 of the batter and mix with the purple sweet potato paste from (2).

9. Pour the two batters into the prepared loaf pan in alternating sequence - adding new scoop of batter on top of the previous one to create the line pattern​.

10. Bake at middle rack of a preheated oven set at 150° Celsius for 40 minutes. Increase the oven temperature to 170° Celsius for additional 5 minutes to give a nicer brown top.

 End of baking

Let the cake cool down in the loaf pan for about 10 to 15 minutes over a wire rack before inverting it out to cool further.

11. Cut the cake after it has cooled down. Enjoy 😋🍰

Purple Sweet Potato Bread (Cold Fermentation) 紫薯吐司

I have a few bread recipes using purple sweet potato. However, this is the first time I used the cold fermentation method for this type of bread.
Breads added with purple sweet potato, has rich antioxidant - anthocyanin (though not sure how much still survived after all the steaming and baking).  It not only gave the bread a nice pinkish colour, but also a soft texture that can last for days.

I used this type of Vietnamese purple sweet potatoes for this recipe.

Yield: one 26x10x10 cm bread 
Breadmaker: Mayer MMBM12
Bread weight: 502 g
Raw dough: about 542 g


60g cold fresh milk
60+10g cold water*

20g beaten egg
35g fine sugar
2g fine salt, 1/4 tsp
20g coconut oil

235g Prima bread flour
100g steamed purple sweet potato paste

1/2 tsp instant dry yeast

* as the liquid content of different origin sweet potato is different, so the additional 10g of water will be added depending on the dough condition.


Some remaining bread flour used for dusting


1. Steamed about 130g of peeled purple sweet potato chunks with pandan leaf (optional) in medium high heat for 20 minuets, or till a thin skewer can poke through easily.

2. Remove the pandan leaves. While the sweet potato is still hot, mash it using a fork. Collect 100g of purple sweet potato paste.

3. Pour ingredients, except the 10g of extra water, into the bread pan following the sequence listed.

4. Place the bread pan back to the bread machine.

Close the lid and select "C-11 Ferment Dough" function, and start the process. Terminate the process manually when the countdown timer reads "0:45".

About 10 minutes after the kneading starts, if the dough is too dry, slowly add in the extra 10g of water.
How to tell if the dough is too dry? If the kneading dough just spin round the axis without the folding action, then the dough is too dry.

5. When the countdown timer reads "0:45", the kneading blade will do about 5 rotations. Stop the process manually after the rotations, by pressing the "Start/Stop" button till you hear a long beep.

6. Coat a plastic bag with a little oil, and transfer the dough into it. Tie a loose knot at the end.

Allow the dough to proof for about 30 minutes in room temperature.

30 minutes later

Add another plastic bag outside, place in a big mixing bowl, close the lid and transfer to the fridge to undergo cold fermentation.
I keep the dough in the fridge for about 18 hours, went in at 1pm and came out at 7 am the next morning.

7.  Transfer the dough out of the fridge about 1 hour before shaping. Remove the outer plastic bag, invert the dough and let it thaw a room temperature for about 1 hour.

8. After thawing, turn out the dough from the plastic bag onto a floured worktop. Flatten the dough to release the trapped air.
It's alright if the dough is still cold.

Fold in the four sides towards the centre.

Flip over the dough, cover with a lid, and let it rest for about 20 minutes.

9. Roll out the dough into about a 1-cm thick rectangular shape. The shorter width should correspond to the longer length of a 26x10x6.5cm loaf pan.

Flip over the dough, so the smoother side would be facing out after rolling up later.

Roll up the dough and, at the same time, pinch the sides to seal.

Coat with some flour and lower into a greased and floured loaf pan.

10. Spray some water over the dough and place it in a closed oven.

Let the dough proof in a warm oven for about 60 to 90 minutes, or till the dough rises to almost 2 to 3 cm above the rim of the pan.
To facilitates the second proofing, you may switch on the oven to its minimal temperature for about 1 minute.

While waiting for the dough to proof, you may want to cut some stencils using parchment paper for decorating the dough later. The pattern is optional.

11. After the second proofing, remove the dough out of the oven. Preheat the oven to 170  degree Celsius.  

Spray a thin coat of water over the paper stencils and "paste" them over the dough surface.

Dust some bread flour over.

Remove the paper stencils and dust another layer of flour over.

12. Bake the dough at the lower rack of the oven at 170 degree Celsius for about 40 to 50 minutes.

13. Remove the bread from the pan immediately after leaving the oven. Let the loaf cool down on a wire rack before slicing it.