Purple sweet potato upside down steamed cake

Yesterday was my third time buying purple sweet potato from the veggie seller. Unlike before, this time I got sweet potato that not purple all around. It has white part in the centre. I don't know anything about sweet potato, I guess it just another variant of purple sweet potato from the one I usually bought. 

While slicing, I kept staring at that nice pattern of the steamed sweet potato. Aha, maybe it will be pretty in upside down cake...don't you think? Lucky me, someone has already made it before, the upside down purple sweet potato cake. I found the recipe at ipoek masak. Ha, it will be easier for me then...Thanks mba Ipuk^^  

I did several changes to this cake. First, I steamed it instead of baked it. I used rice flour instead of wheat flour to make it a gluten free cake. I also omitted the baking powder and emulsifier. It was still nice and moist...with a strong sweet potato taste.

Ingredients:

For the cake:
2 eggs
60 gr caster sugar
1/2 tsp vanilla extract
1/4 tsp emulsifier ( I didn't use it)
60 gr plain flour, sifted ( I used rice flour)
1/2 tsp baking powder (I didn't use it)
150 gr sweet purple potato, steamed and mashed
2 tbs milk
30 ml oil/ melted butter
50 gr white cooking chocolate/chips, chopped
50 gr cheddar cheese, grated

For topping:
1 sweet purple sweet potato, steamed and slice round
30 gr cheddar cheese, grated

Methods:

1. Heat enough water in a big pan.
2. Grease a 18 cm round baking tin with oil and dust with a little flour.
3. Arrange purple sweet potato on it and add the grated cheese around the sweet potato.
4. When the water already hot enough. Off the stove and remove the pan to the table. Place the eggs and sugar on a heatproof bowl. Put the bowl in the pan with hot water. Beat on low speed until the sugar dissolve. Remove the bowl from the heat. Increase the speed to high, beat again until thick and pale.
5. Lower the speed again, add in the mashed sweet potato and milk. Beat again until well incorporated. Off the mixer.
6. Heat again the water in the pan. Place a steamer on it.
7. Add the flour in the batter while sifting in 3 batches. Fold it carefully.
8. Remove some of the batter to a bowl. Pour in the oil. Fold it slowly and carefully until well incorporated.
9. Pour it back to the batter. Fold it well. Add in the grated cheese and chocolate chips. Fold again until all well incorporated.
10. Pour the batter in the baking tin and steam for 25 - 30 minutes. 
11. Remove from the steamer. Let stand for about 10 minutes. Then invert the cake onto a plate.
12. Enjoy!

I am submitting this post to aspiring bakers #25 about steaming hot cakes hosted by Miss B of everybody eats well in Flanders.