2. Materials: eggs, low-gluten flour 100g, corn oil 70g, refined sugar 70g, yogurt 130g, cocoa powder 15g.

3. Practice: Break up the eggs, separate the egg yolk protein, and prepare 65g egg yolk, with protein 175g. Break up the egg yolk, add 50g fine sugar and 70g corn oil to the egg yolk, continue to stir evenly, then pour in 130g yogurt and stir until it is viscous and emulsified. 100g low-gluten flour is sieved into the batter and stirred until the batter thickens and the yolk paste is ready. Stir the egg whites until they have coarse bubbles, add 20g fine sugar twice and beat until they have small sharp corners. Take one third of the egg white cream and put it into the yolk paste. After stirring, pour it into the remaining egg white paste and stir it up and down evenly to make batter. Take 300g of batter, sieve in 15g of cocoa powder, and stir evenly to make cocoa batter. Take a 16 inch mold and put the white batter and cocoa batter into the middle of the mold several times with a spoon. Preheat the air fryer, heat it up and down 160℃, bake it for 30 minutes, cool it, demould it, and cut it into pieces with a serrated knife.