Carefully crack the eggs, separating the whites and yolks into two clean, dry, and oil-free bowls. Ensure no yolk gets into the whites, as this can affect whipping.

Add a few drops of lemon juice to the egg whites to reduce any odor and stabilize the meringue.

Use a hand mixer at low speed to beat the egg whites. When large bubbles (fish-eye size) appear, add 20g sugar for the first time.

Continue whipping at medium speed until the egg whites double in volume and develop a fine, frothy texture. Add the remaining 20g sugar.

Whip at high speed until you see clear ridges forming. When lifting the whisk, the meringue should form a straight peak. Add 10g cornstarch at this stage.

Finish with low-speed whipping to mix the cornstarch evenly. The final meringue should be smooth, glossy, and stable, with slightly bent peaks.

Use a whisk to beat the egg yolks until their color lightens and the texture becomes smooth and creamy.

Gently fold one-third of the meringue into the yolk mixture using a spatula. Mix from the bottom up while rotating the bowl to prevent deflation.

Pour the yolk mixture into the remaining meringue and fold until the batter is smooth, fluffy, and uniform. Be careful not to overmix.

Place the paper liners into the 25-cup baking mold.

Transfer the batter into a piping bag (or use a spoon) and fill each liner to 80% full. Ensure even distribution of the batter.

Sprinkle black sesame seeds evenly on top for added aroma and texture.

Preheat the oven to 135°C (top and bottom heat).

Place the mold on the middle rack and bake for about 28 minutes.

Check the cupcakes during baking. If the tops brown too quickly, cover with foil to prevent burning while ensuring the centers bake through.

Test for doneness with a toothpick. If it comes out clean, the cupcakes are done. If wet batter sticks, bake a little longer while monitoring closely.

Remove the cupcakes from the oven and cool on a rack for a few minutes.