Pengqi is type of crab but is not a good crab, it’s small about 3-4 cm, like to eat soil and also bad smell so usually is uneatable. In my family we catch them in winter because they start not eat food and raise with clean water about a week and remove the tail than add salt, sugar, red distillers grains, cooking wine, MSG and other spices. Pickling for a while than stone grinding into a sauce that is how we do it, than we call it Pengqi sauce or crab sauce usually for dipping when we smell have very rich and fresh wine smell and when we taste is salty with little sweet and more. Now this sauce has become a rare thing even in China is hard to buy one that rich, fresh sauce. My mom get one for $20 in America I don’t where but is not that rich, fresh but still reminds me of home, the time I catch crab with my family until I caught by crab than I always look them to do it. I hope sauce formula not be lost in future so my family and my children can taste it because it’s a good sauce or good food, taste good and health.