Banana Walnut Sponge Cake

This recipe was recommended from a youtube source and it was recommended by a friend and I have baked it a few times and like it a lot, as it feels very light.

Recipe
150g Ripe Banana (mash it) 4 Egg Yolks (separate from egg whites) 40g Vegetable oil (I used red palm Oil), preheat it for about 15 minutes until it is warm 20g Fresh Milk, full cream is better 85g I used normal flour 4 Egg whites which was separated from from the egg yolk earlier 60g Sugar (I used about 30gm because I do not like a very sweet one A handful of Walnut (chopped it, and if you like it more, add more).

Steps:
1) mash the banana, put aside.
2) The preheated oil, add in 85gm flour and stir well. Then add in the egg yolk, milk and mashed banana, mix it well.
3) Beat egg white with sugar (dividied into 3 times) and beat it until it well, until it is kind of becomes very stable (and it won't flows freely if you overturn the mixer bowl).
4) Mix in this into 3-step a portion each into the premixed mentioned in step 2. Stir well.
5) Prepare a baking mold and it will be good to line up with a layer of baking paper. Then pour the batter into the mould and then flatten it.
6) Then put this mold into a water bath

7) Then bake it at preheated oven of 150 Deg C for 1 hour at least or until it is fully baked. Take it out and let it cool.
8) when you tap on the well baked cake, it sound fluffy, or spongy.

Choong