2. After boiling, pour it into a bowl to cool

3. Beat the egg whites and break them up

4. At this time, the milk is cold, and the surface is covered with milk skin

5. Lift a corner of the milk skin and pour it back into the pot and add sugar to beat it evenly (be careful not to break the milk skin, but leave it on the bottom layer of the bowl)

7. At this time, pour egg white (one big egg and two small eggs) into the big bowl, and add some sugar and stir. When the milk in the small bowl cools, carefully pierce the skin and slowly pour the milk into the big bowl. If handled properly, the milk skin will lie safely at the bottom of the small bowl. Ok, stir the egg whites, sugar and milk in the big bowl evenly, and then slowly (definitely) pour them back into the small bowl. If the operation is done properly, the milk skin at the bottom of the original small bowl floats and covers the mixture. Put into the pot and steam. Timely take out the pan, cool, and generate new milk skin. It means double skin milk.