Adapted from mymindpatch.
All ingredients in room temperature
85g unsalted butter, softened
50g fine sugar
3 egg yolks
1/2 tsp vanilla extract
3 egg whites
35g fine sugar
85g cake flour
1/2 tsp baking powder
1/8 tsp salt
30g fresh milk
2 tsp cocoa powder
1. Mix cake flour, baking powder and salt together. Set aside.
2. Whip butter till pale. Add in sugar and continue to whip till light and creamy. This takes about 5 minutes.
3. Add in the 3 egg yolks and beat together.
4. Beat egg whites in a clean and grease-free mixing bowl till frothy. Gradually add the sugar and beat till firm peaks formed.
5. Add the vanilla essence into the egg white mixture and blend well.
6. Gradually fold the egg batter into the whipped butter in step 3.
7. Sieve in 1/3 of the flour mixture from (1) into the batter. Fold in the flour using a spatula. Do not over mix. It’s okay to have streaks of unmixed flour as the subsequent mixing will do away with it.
8. Add in 1/2 of the fresh milk.
9. Finish up the remaining flour mixture and milk by adding them alternatively.
10. Take about 1/5 of the batter to mix with the cocoa powder.
11. Pour the butter-egg batter and cocoa batter in alternative pattern into the lined cake mould.
12. Run a stick or chopstick in spiral motion to create a swirl pattern.
13. Bake in a pre-heated oven at 180 degree Celsius for about 35 to 40 minutes, or till an inserted skewer came out clean.14. Allow the cake to cool down in the oven before cutting and serving