Tuesday, September 15, 2015

Purple sweet potato butter cake

It is almost like an alarm clock in the body. I would naturally crave for some butter cake or poundcake like bakes time to time. Do you get that too? Yes, I love chiffon, I love tarts, I love pastries, but somehow the lure of buttery soft cake keeps coming back for more! Although having the good old traditional butter cake is the best, I still enjoy explore and experimenting different ingredients being incorporated to it. And this time is none other then one of my favourite sweet potato...not just any, but that sweet and pretty purple sweet potato. And so Purple Sweet Potato Butter Cake is born!
The addition of the root vegetable has made this cake not only more moist, it also gives off that sweet potato aroma and flavour when you eat it, especially when it is warm. So love! If you love pumpkin too, you can try it with that. But keep in mind that pumpkin has more water content verses sweet potatoes, so the result might end up a wee bit different perhaps.

For now, let's look at this Purple Sweet Potato Butter Cake recipe and see what it consist. :)

Ingredients for Purple Sweet Potato Butter Cake (makes a 8" by 8" square)
150 g sweet potato steamed + 50 ml coconut oil 
  •  Blend the two together until smooth. Set aside for use later

Egg Yolk Batter
5 egg yolks (~73-75g)
60g caster sugar
200 g salted butter at room temperature (Or unsalted butter with 1/2 tsp salt)
200 g cake flour

Egg White Batter
5 egg white
100 g caster sugar
1 tsp fresh lemon juice

  • Preheat the oven to 155C. Prepare a steam bath in the bottom rack so you can so a steam bake later. Grease and line a 8" by 8" square pan with parchment paper. Set aside for use later.
  • In a large mixing bowl, add in the yolks and caster sugar. Start whisking till it thickens and doubled its volume.
  • Next place the softened room temperature butter in, whisk it in in gently to the yolk batter. The batter will be thick and creamy.

  • Now you can add in the blended sweet potato and coconut oil puree. Again, give it a good whisk to combine thoroughly.
  • Last, add in the sifted cake flour. Whisk well again.

  • Next, whisk the egg whites in another mixer bowl. Add in the lemon juice  and then gradually the caster sugar and continue to beat till stiff peaks.

  • In 3 separate portions, add in the egg whites to the egg yolk batter, folding gently each time and careful not to deflate the egg whites.

  • Pour the batter into the prepared baking pan, spread it evenly. At this moment, you can choose to bake it as is or put on the extra sweet potato cream topping swirls.

Swirl Topping (optional)
100 g sweet potato + 60 ml heavy cream
  •  Blend the two together until smooth. Set aside for use later

  • Scoop spoonfuls of the sweet potato cream puree over the top of the cake batter. Then using a tooth pick, run it through the batter to create that swirl effect.

  • Steam bake the cake in the preheated oven for 55-60 minutes in the water bath till the cake tester or toothpick comes out clean. 

  • Once baked, carefully remove from the oven and place over a towel. Remove the cake from its cake pan and cool on the rack completely before slicing. Enjoy!

See...it's not that complicated right? Although I did add sweet potato in both the cake batter and as a topping. I think it adds that extra oomph and sweet potato intensity to it.

With the addition of coconut oil, it really brings out the coconut fragrance. A little goes a long way! And that purple sweet potato cream swirls not only beautifies the cake appearance, it also adds that creamy sweet potato bite, which is like a bonus every time!

A close look at the soft cake texture of this special butter cake. :9 It is not dense at all, moist and fragrant and also buttery rich that leaves you satisfied. Or maybe you're like me...I can't resist having 3 slices at one go... oops. :P

If you decide to give this a try, try making it ahead and let the cake rest overnight. I personally feel the cake taste better the following day. Just like any butter cake, the taste mallows out and somehow makes it more rich in taste and flavour the following day. Like magic...taste like magic too. Don't take my word for it, get your baking apron on and try it yourself. ;)

Okay guys, signing off now. Hope you all will like this recipe and drop me a note if you did try it ya? 

Remember, do what you love and stay happy!


Unknown said...

Hi! Do you think using the normal orange sweet potato would work just as well? :)

Unknown said...

Hi! Do you think using the normal orange sweet potato would work just as well? :)

Angie's Recipes said...

The use of purple sweet potato gives this butter cake a special touch. YUM!

My Little Space said...

Bee, love your first picture a lot. The cake looks simply irresistible.
Have a great week ahead dear.
Blessings, Kristy

Honey Bee Sweets said...

Hi Carissa, You can try using orange sweet potato too. I think it should work.

Honey Bee Sweets said...

Thanks Angie! I love sweet potato. :9

Thank you Kristy! Have a good week ahead too!

Anonymous said...

Hi! Is there any other oil to replace the coconut oil?

Honey Bee Sweets said...

Just use normal vegetable oil. But the end result will not be as fragrant for sure.

Anonymous said...

Hi, is it possible to use whipping cream instead of heavy cream?

Honey Bee Sweets said...

Yes you can try that, use whipping cream.

Anonymous said...

Hi, I tried your recipe today.
And it was really good!
I used orange sweet potato instead of the purple one.
But my cake looks very compact. There's not as many air bubbles as yours.
Do you know what went wrong?

jenn said...

Do I need to keep the in the fridge if I could not finish it in a day or is it okay to leave it in room temperature overnight?

Honey Bee Sweets said...

hi Anonymous,
Frankly speaking when I get this kind of question, I really don't know what went wrong. All I can guess is your egg whites are not beaten properly or your oven temperature is nit right or maybe you over mixed the cake batter? Anyway, this is a very common technique used in baking, egg white + egg yolk batter to yield fluffier texture. Hope the next time you try something similar, you can take note of it.

Hi Jenn, I am not sure of your home temperature. Is it warm in general? Do you keep your cake in an airtight container? I would usually put in the fridge the following day.