Okinawan Purple Sweet Potato Cake

I made this cake for two ladies who comes to my basket group to celebrate their birthday.  I'm not sure how Purple Sweet Potatoes are available in your area but in Indianapolis, you can find them most of the time at Asia Mart near Castleton Mall.   You can also use Asian Sweet Potatoes but I'm not too sure about the yams or the stuff America calls sweet potato.   Yams are way too watery and squishy in my opinion.  

I bake the sponge first:

Base recipe: 1 egg, 30gm sugar, 30gm cake flour, 10gm butter, 10ml milk, drop of vanilla extract.    Multiply the base recipe to make enough batter for the size of cake pan you plan  on using.               7" round uses 3 eggs, 8" uses 5eggs,  9" use 7 eggs. prepare your pan by cutting parchment paper to fit and line the pan.

preheat oven to 335F

beat eggs and sugar













whip like crazy until it turns thick and white

sift cake flour 2 X and set a side.
melt butter set aside

add the sifted flour and mix gently making sure you didn't leave any flour unincorporated, add butter.  Pour the cake batter into prepared pan, and bake in 335F oven for 20mins.  touch the cake and and if it springs back, its done, take it out of the oven and drop it on  your counter from about 6-8inch above the counter top. (this keeps the cake from shrinking)

cool on wire rack for about 5 min then take it out of the pan, peel off the parchment paper and cool until easy to handle.



While the cake bakes make the sweet potato cream.  boil the potatoes whole to keep the color from bleeding out. once soft  peel while its hot, puree in food processor, adding 3tbsp butter and add some heavy cream maybe 2 tbsp? all depends on how your thick your potato paste is.  if its too thick add more cream.  You don't want to add too much! it should be pasty but not runny.

once completely cool, slice and half  

Make quick custard cream while cake cools
2 egg yolks
40 gm sugar
20gm flour
180ml milk
drop of vanilla
1 tsp butter

mix egg and sugar well in a microwaveable bowl, add flour and mix until smooth.  add milk little at a time while mixing with a whisk until all milk in incorporated and liquid  is smooth.  microwave uncovered  for 1 min, take it out of the microwave, mix well, microwave again for 30sec-1min.   custard should be thick and smooth, add butter and vanilla mix until butter  melts and vanilla is incorporated. put plastic wrap on the custard  to keep it from forming skin.

when cake and custard are cool, gently place bottom slice of cake on a plate of your choice, spread or pipe custard on top of the cake, place top slice of cake on top of custard.







cover the cake with whipped cream.



*2 cups Heavy cream, sugar to taste and 2 packages of Whip it and whip it until hard peaks! don't over do it or you'll end up with butter!!

I use this piping tip to decorate the cake.  its like a giant grass tip

decorate it with purple sweet potato cream

Happy Birthday!