Soak the raisins in clean water for 15 minutes, then drain well and set aside.

Line a baking tray with parchment paper, making sure it fits snugly against the sides.

Separate the egg yolks and egg whites into two bowls.

In a large bowl, combine the milk and corn oil. Whisk thoroughly until fully emulsified, with no visible oil droplets.

Sift the cake flour directly into the mixture and gently mix using a straight-line motion until no dry flour remains. Avoid circular stirring to prevent gluten development.

Add the egg yolks and continue mixing with the same motion until the batter is smooth, fine, and lump-free. Set aside.

Place the egg whites and vinegar or lemon juice into a clean, dry, oil-free bowl.

Using an electric mixer on low speed, beat for about 30 seconds until fine bubbles form.

Add the sugar in three additions:

First addition: beat on low speed until the bubbles disappear

Second addition: beat on medium speed until fine lines appear

Third addition: beat on high speed until soft peaks form

The meringue should form a large curved hook when lifting the whisk and should not slide when the bowl is inverted.

Fold one-third of the meringue into the egg yolk batter using a spatula, lifting gently from the bottom up to loosen the mixture.

Pour the combined batter back into the remaining meringue and fold gently but quickly until no white streaks remain and the batter looks smooth and glossy.

Evenly scatter the drained raisins over the lined baking tray.

Pour the batter onto the tray from about 20 cm above, then gently level the surface.

Tap the tray lightly 3–5 times to release large air bubbles.

Preheat the oven for 10 minutes.

Bake on the middle rack at 150°C top heat / 145°C bottom heat for 30 minutes, until the surface is lightly golden and springs back when pressed.

As soon as the cake comes out of the oven, carefully lift it (using the parchment paper) onto a cooling rack. Let it cool for only 2-3 minutes, until it's just cool enough to handle but still very warm and pliable.

Place a fresh, clean piece of parchment paper (larger than the cake) on your counter. Carefully invert the warm cake onto this new paper and peel off the baked parchment layer from the bottom (now the top).

While the cake is still warm, start rolling it from one of the shorter ends. Use the new parchment paper to help you roll, creating a tight spiral. Don't press too hard.

(For a detailed rolling technique, refer to my Pork Floss Roll Cake tutorial.)

Refrigerate for 20 minutes to set, then slice into pieces about 5 cm wide and serve.