Sift together 85g cake flour, 15g cornstarch, and 20g cocoa powder.

Heat 90g corn oil over low heat to about 70°C (a bamboo skewer inserted should form small bubbles). Immediately remove from heat and pour in the sifted dry ingredients. Stir quickly to form a smooth paste.

Add 80g milk and mix until fully absorbed.

Add 8 egg yolks and gently mix until smooth and combined. Do not overmix to avoid developing gluten.

Add a few drops of lemon juice to 8 egg whites, beat on low speed to break them up, then switch to high speed.

Gradually add 80g sugar in three batches:

First when large bubbles appear

Second as the bubbles tighten

Third when streaks start to form

Beat to soft peaks – the meringue should form elastic peaks that curl slightly.

Add 10g cornstarch, and mix on low speed for about 10 seconds to stabilize the meringue.

Take 1/3 of the meringue and gently fold into the yolk batter. Reserve a small amount of yolk batter for decoration.

Pour the mixture back into the remaining meringue and gently fold until the batter is smooth and evenly colored. Do not stir in circles—fold from bottom to top to avoid deflation.

Line the bottom of your baking mold with parchment paper. Pour in the batter and tap the mold gently to release air bubbles. Smooth the surface.

Mix the reserved yolk batter with a little cocoa powder, place it in a piping bag, and draw stripes on top. Use a toothpick to drag lines and create a feather or "flower" pattern.

Place the mold on a baking tray. Pour hot water into the tray until it reaches 2/3 the height of the cake mold (for steam baking).

Preheat oven and bake with top heat at 150°C and bottom heat at 160°C for 60 minutes.

(Tip: In the last 5 minutes, open the oven to check. If the surface is golden and springy, it's done. If cracks appear early, your temperature may be too high.)

While hot, lift the cake out using the parchment paper. Peel off the paper, cut into slices while warm, and enjoy!