Whisk the yolk lightly, add sugar and whip. I put in brown sugar because I thought it would be more moist. Whip it until it turns white and holds the whisk until the ribbon marks don't disappear for 3 to 4 seconds.

Add room temperature milk and mix.

Sift together the flour and cocoa powder. Add the powder and mix using a spatula or whisk to ensure that there are no lumps.

Place the whites in another bowl, whisk and add sugar and top with meringue.

Please make a hard meringue with horns.

Mix 1/3 of the meringue in the yolk mixture, then add the remaining 1/3 and add the last remaining meringue and mix lightly so that the meringue does not lump. Be careful not to let the meringue bubble burst too much. When you're done mixing the meringue, pour the batter into a chiffon mold with water spray, stir once or twice with chopsticks to remove large bubbles and bake at 160'c for 20 to 30 minutes.