Bring the eggs to room temperature. Combine the flour with matcha, and sift 2 to 3 times. Line the cake pan with parchment paper. If you grease the pan slightly, the lining will stick.
Microwave the milk and butter in the same container. Make sure the butter is completely melted. Preheat the oven to 170℃.
Crack the eggs into a bowl, and add the sugar. Warm the bowl over warm water at about 60℃, and whisk with a hand-held mixer in high speed.
When the eggs are about 36℃ (slightly warm when tested with your fingers), remove from the warm water and continue to whisk at high speed. Use the same warm water to keep the temperature of the milk and butter.
When it gets thick and creamy. This usually takes 5 minutes after placing the bowl over warm water. Continue to whisk at low speed for about 3 minutes.
It gets glossier than when whisked at high speed.
Change the whisk. Add 1 tablespoon water and whip lightly. By adding water, it makes the powdered ingredients blend easier.
Add all powdered ingredients in one go. Whip about 30 to 35 times.
Remove the milk and butter from the warm water. Mix in a small portion of the mixture from step 8. This makes it easier than adding the milk and butter directly into the mixture.
Add the mixture from step 9 into the bowl from step 8. Use a rubber spatula to cut in and blend. Make sure it gets creamy and glossy.
Pour the mixture into the cake pan.
Bake for 30 to 35 minutes in the 170℃ preheated oven.
Test with a skewer. If it doesn't come out clean, bake for another 5 minutes. Watch the cake as you bake.
When it's done, drop from about 20 cm above your workplace. This prevents any shrinking.
Turn it upside down and remove from the pan onto a rack. Peel any parchment paper. Cover with a damp cloth and let it cool.
When it's completely cooled down, put it in a plastic bag and chill in the fridge for about half to one whole day.
Story Behind this Recipe
I made this matcha sponge cake to make a matcha dome cake.
If the warm water to warm the milk and butter cools down, make sure to bring it back to approximately 60℃. You shouldn't mix too much at step 10, but if you don't mix it just right, the butter will sink. You could use regular letter paper instead of parchment paper.