Puff is a kind of cake cake, usually made of flour, butter, water, eggs and other materials. The reason why the puff is hollow is that during baking, the moisture in the dough will evaporate, forming bubbles, which will expand the puff and finally form a hollow structure.
Specifically, in the process of making puffs, flour, butter and water are mixed to form a dough. Then add the eggs to the dough one by one, and keep stirring to make the dough soft and elastic. During the baking process, the moisture in the dough will be heated and evaporated, forming bubbles, which will cause the dough to expand. As the dough of puff is relatively soft, the bubbles can easily expand to form a hollow structure.
Therefore, the reason why the puff is hollow is that during baking, the moisture in the dough evaporates to form bubbles, which makes the puff expand and finally forms a hollow structure.
