Pandan Paper Sponge Cake

Recipe original source is from 'food for life tv'. Following, I had reduced the recipe and made some adjustment to it.

Recipe

Ingredients
3 egg yolk
25g veg. oil
1/4tsp salt
40g pandan juice
20g milk
1/4tsp pandan paste
75g self-raising flour
1/4tsp salt

3 egg white
50g sugar
1/4tsp cream of tartar

Steps:
1. Preheat oven to 170C.
2. Lined muffin cups with cut out grease proof paper 14cmx14cm and set aside.
3. Sift flour and salt together, set aside.
4. With a hand whisk, whisk egg yolk and oil together till blended.
5. Add in pandan juice, pandan paste and milk, whisk till blended.
6. Add in flour and stir till batter is smooth.
7. Use a cake mixer, whisk egg whites and cream of tartar till frothy.
8. Gradually add in sugar and whisk till stiff peaks form.
9. Fold in 1/3 of the meringue into egg yolk batter until blended.
10.Lastly, fold in the rest of the meringue lightly in two portions till blended.
11.Pour batter into piping bag.
12.Pipe batter into prepared cups till 70% full.
13.Tap each cup on tabletop to burst air bubbles in the cake batter.
14.Bake in preheated oven for 25-30mins.
15.Switch off oven power, allow cakes to sit in oven for 5-10mins with oven door slightly opened.
16.Remove cakes from muffin cups and cool on a wire rack.