Spiku aka kue lapis Surabaya

I always like to buy spiku from 'Kedai Kue-kue' at Bugis Junction. Price $8.50 half size. Until one day Cynthia told me that she could remember the recipe for this spiku and her family love them, so she gave me this recipe over the phone. She told me, two of her friends have ever tried this recipe but the cake couldnt rise/expand well ('bantet'), hmmm... it made me a bit worry of my result. I quickly searched for spiku recipe over internet, compare with Cynthia's and manage to get some tips on baking this cake.

Using normal flour, no baking powder, I had discouraged at the beginning. But finally I made quick decision to try it! This recipe using 30 egg yolks, if failed, wow! Bought the 30 eggs from Phoon Huat (made me shocked, when realised the price is $7 for 30 eggs while in Fairprice actually I could get them just $4.80 for 30 eggs), but later on I realised the difference lays at the egg yolks which truly very red, great for baking cake like this spiku.

I need to bake three times for three layers, as I only have 1 pc of 'baking tin square pan'. Luckily all three layers baked perfectly, very yummy! We love the taste, thanks to Cynthia for sharing this great recipe!

Ingredient for yellow layer:
10 egg yolks
100 g fine sugar
5o g flour
100 g butter (combination is better, means 50g unsalted butter + 50g margarine)
1/4 tsp vanilli powder

Ingredient for chocolate layer:
10 egg yolks
30 g flour
20 g chocolate powder
100 g butter (combination is better, means 50g unsalted butter + 50g margarine)

For next bake:
I need to learn how to make the top layer after each baking, will be smooth. (as you noticed from the pic, the top layer not smooth enough)