Sift the powdered ingredients. Preheat the oven to 170℃. Line the cake pan with parchment paper.
Put the eggs and sugar in a bowl and heat in a 50℃ double boiler. Once it becomes warm to the touch, remove from the double boiler and beat (until it reaches the stage where you can draw an S on the surface).
Beat until it becomes thick and white, sift the drt ingredients again, and fold into the batter in 2-3 portions.
Warm the butter and milk in the microwave and quickly mix it all together (the butter will melt at about 40-50℃).
Pour the batter into the cake pan and lightly drop the cake pan on a table to release the air. Bake in an oven at 70℃ for 30-35 minutes.
Once baked, remove from the cake pan and peel off the parchment paper. Let cool on a rack.
Adjust the temperature and time to your oven. Keep an eye on it as it bakes.
Step 2: Beat until the batter forms ribbons when lifted.
Step 6: If a skewer or toothpick pushed into the center comes out clean, it's done baking.
Story Behind this Recipe
This is a sponge cake I've made for a long time. If you would like a chocolate sponge cake, reduce the flour by about 10 g and add about 20 g of cocoa.
Step 1: If using an electric mixer, beat on high speed until you can draw an S on the surface of the batter, about 1-2 minutes. Step 4: If the temperature of the melted butter is too high, it will remove all the air from the batter and result in a deflated cake.