First preheat oven to 355 degrees F (180 degrees C).
Then line muffin pan with parchment paper.
Separate yolks and whites of Egg (5). Add Vanilla Essence (1/4 teaspoon) into egg yolks and whisk till combined. Then set aside.
In a large measuring cup or bowl, combine Butter (50 gram) and Milk (60 milliliter). Mix with a whisk. Then sieve in All-Purpose Flour (100 gram). Continue to mix well.
Add in the egg yolk mixture. Mix again till smooth and set aside.
Next, beat egg whites in a clean mixing bowl with low speed until bubbles formed. Then, add Granulated Sugar (80 gram) a little at a time, 3 portions, and beat until soft peaks formed.
Then lightly fold the beaten egg whites in 3 portions into the egg batter.
Pour the combined batter into the lined muffin pan till 3/4 full. Next, bake in the preheated oven for about 20 to 25 minutes until a toothpick inserted in the middle comes out clean.
Once cooked, remove from oven and cool on wire rack for 5 minutes. Lastly remove the baked sponge cake to cool completely on wire rack.
Serve these super soft and fluffy chinese sponge cake for afternoon tea or anytime you desire. Enjoy!