Mao xue wang (毛血旺, literally 'hair blood prosperous') is a Chongqing street dish of extraordinary richness and complexity — a large bowl of duck blood tofu, tripe, pork lung, eel, tofu, bean sprouts, and other ingredients simmered in a mala-spiced broth and topped with a generous pour of sizzling chilli oil. It is named for the blood tofu (xue wang, 血旺 — duck or pork blood set into a custard-like block) that is its primary ingredient. The dish is the quintessential Chongqing street food — cheap, sustaining, intensely flavoured, and made from the offal and by-products that represent the resourcefulness of Sichuan cooking.
The blood tofu: Duck or pork blood mixed with salt and water is allowed to set into a soft, jelly-like block. It has a mild, slightly metallic savouriness that absorbs the mala broth. Slice into rectangles for use in mao xue wang. The broth: Similar to the Sichuan hot pot broth but slightly less intense — doubanjiang fried in oil with dried chillis, Sichuan peppercorn, garlic, ginger, and spices. Diluted with stock. The broth should be heavily red from the chilli oil. The assembly: The main ingredients — blood tofu, tripe, bean sprouts, tofu skin, eel — are simmered in the broth in order of cooking time. The blood tofu and bean sprouts last (they only need 2-3 minutes). The assembled dish is topped with sliced scallion and a generous ladle of pure chilli oil, which is ignited briefly at the tableside in some restaurants.
Fuchsia Dunlop, The Food of Sichuan (2019)