Purple has always been my favorite color, so it’s only befitting I combine it with another of my all-time favorite cake – chiffon cake. It also helps that I found a bottle of purple sweet potato powder at Kitchen Capers but it is totally an optional ingredient.
The purple sweet potato powder gives the Purple Sweet Potato Chiffon Cake that extra purplish pink hue which I find it really mesmerizing. Without it, the earthiness from the purple sweet potato still comes through really well in the taste department.
120 g purple sweet potato – boiled and mashed
3 tbsp milk
1 tsp purple sweet potato powder (optional)
3 egg yolks (I’m using 60 g eggs)
30 g sugar
1/8 tsp salt
50 ml vegetable oil
3 tbsp water
85 g cake flour
The line up.
4 egg whites
60 g sugar
½ tsp cream of tartar
Bring a pot of water to boil and add in sweet potato. Boil for 15 – 20 mins until soft.
Allow it to cool slightly before peeling off the skin. Put the peeled sweet potato and milk into a blender and pulse into paste. Alternatively, you could mash it manually with a fork.
In a large mixing bowl, add in egg yolks, sugar, salt and whisk until pale and fluffy.
Add in water, vegetable oil and mix until combined.
To the mixture, add in sweet potato paste, sweet potato powder (if using) and mix until well incorporated.
Sift in flour and fold into the batter until the flour just disappear.
In a clean large bowl, add in egg whites, cream of tartar and whisk until foamy. I highly recommend using a handheld blender or stand mixer for this job.
With the beater still running, add in the sugar slowly and whisk until stiff peaks.
Add ⅓ of the meringue to the sweet potato batter and fold gently. Repeat with the rest of the meringue.
Tap the bowl a few times lightly on the counter to release large air bubbles.
Pour into an ungreased chiffon cake tin and smooth the top with a spatula.
Bake in a preheated oven at 170C/320F for 15 mins and turn down the temperature to 140C/290F and bake for another 20 mins or until a skewer inserted comes out dry. *Cover the top loosely with an aluminum foil if the cake is browning too fast.
Remove from oven and immediately set the cake tin upside down on top of a glass or bowl. Make sure it is not too low and near the counter surface. Place a damp cloth on the tin to speed up the cooling process.
Let it cool completely before unmolding.
Run a thin knife or offset spatula around the edges and base of the tin.
Gently slide the cake out and place on serving tray.
The cake could be kept at room temperature for 3 days or in the fridge for up to a week.