Is the middle of the pot as flat as the periphery?

Not equal to flat. The middle of the pot is not as flat as the periphery. Protruded in the middle, deep around. This is because when making fried dumplings, first pour oil into the pot, then put the steamed bread in when the oil is hot, and then add water to boil it. After the water evaporates, the oil at the bottom of the pot begins to heat up, making the bottom of the fried dumplings at the bottom of the pot crispy. The steamed stuffed bun in the middle of the pot was not stained with oil, so it didn't become brittle, but kept its original shape. Shuijianbao, a traditional snack, belongs to Henan cuisine. It has a history of more than 500 years. It originated in the capital city of Tokyo (Kaifeng, the ancient capital) and is quite popular in North China and the Central Plains.