Separate egg yolks from egg whites.

Whisk egg whites until foamy. Add sugar in batches and continue whisking.

Add vinegar and whisk until it reaches firm peaks.

Add cooking oil and milk to egg yolks. Beat egg mixture until pale yellow.

Sift in cake flour, baking powder and salt. Fold until well combined.

Add ⅓ of the meringue to the egg mixture and fold gently.

Transfer the egg yolk mixture to the rest of the meringue and mix gently until well combined..

Pour the cake batter slowly (to break up air bubbles in batter) into a 20 cm chiffon baking pan. Do not grease the pan. Run a chopstick through the batter to help release bubbles. Tap the baking pan on the table firmly to release trapped air bubbles.

Bake in a preheated oven (lowest rack) at 170 C for about 50 minutes. To prevent from browning too fast, cover top with a baking pan placed on an oven rack (as shown in the video) mid way through baking. Or you could cover with baking paper.

Remove pan from the oven and test by inserting a skewer into the cake. If it comes out clean then cake is done.

Invert the pan immediately and leave it to cool down. Unmould the cake by running a thin spatula round the sides to separate the cake from the pan. Also insert the spatula round the tube of the pan. Invert the pan and cake will slide out or you may need to press the base to release the cake. Run spatula along the base to remove the cake.