Reason: 1. When the cake is taken out of the high-temperature oven, it will shrink to a certain extent because of thermal expansion and cold contraction.

2. protein is not evenly mixed. When egg white and yolk powder are mixed together, follow the principle of cross mixing and stir quickly.

Cake baking: materials: eggs, low-gluten flour, fine sugar, pure milk, salad oil.

Step: 1. Put 5 egg whites into an egg beater and beat with electric egg beater until coarse. Add fine sugar at this time. Continue stirring until it dries and bubbles.

2. Put 5 egg yolks and 30 grams of fine sugar into another eggbeater and beat them evenly with a manual eggbeater until the color of the egg yolks becomes lighter. Then add salad oil and flour and stir well.

3. Pour the batter into the cake mold and lick it gently on the table to shake out the big bubbles in the cake paste.

4. Preheat the oven for 10 minutes, put the cake in the middle layer of the preheated oven and bake at 170 degrees for 40 minutes.