Pudding has air holes when it is baked, which may be because the foam on it is not filtered out with a small net after the egg liquid and milk are stirred; It may also be that the eggs used are too fresh and the baking temperature is high. Fresh eggs contain a lot of carbon dioxide. When heated, the carbon dioxide in the eggs will overflow and solidify. But if the heating temperature is too high, the pudding liquid will solidify and become a small hole before the carbon dioxide overflows.