Lamb Blood and Vermicelli Soup

Lamb blood and vermicelli soup grew out of the lamb cookery of the Hui Muslim quarter of Xi'an, where the day's slaughter left fresh blood to be used. It is one of three local ways with lamb blood, alongside the cold-dressed 辣子蒜羊血. By one account it was refined early in the twentieth century from a rougher street preparation by a blood-stall keeper near Nanyuan Gate (南院门) named Wang Jintang (王金堂), but other sources describe it simply as a folk dish later taken up by cooks in the market, and the exact originator and date are unrecorded. What is consistent across accounts is the method: blood set with salt and water, a spice-built broth, and the dish eaten soaked with torn flatbread in the manner of Xi'an's lamb-soup tradition.

The blood comes in soft strips the size of matchsticks, glossy and just-firm, sliding apart on the tongue without any grain or rubberiness when it is fresh and gently cooked. Around it the broth is thin and clear-tasting but deep with lamb, prickling with Sichuan pepper and warm with fennel and the other spices; the vermicelli is slippery, the green garlic sharp, the chili oil a red film of heat and fragrance on top. The torn flatbread soaks up the soup yet keeps a little chew. Done badly, the blood is coarse, full of holes, and bouncy from too much salt or too hard a boil, the broth either bland or sour with stale spice.

The blood is a protein gel. Fresh lamb blood is whisked with salt and an equal measure of cold water, then left undisturbed: the salt's ions help the blood proteins (chiefly albumin and globulins) link into a network, and the dilution keeps the set soft rather than dense, so the curd holds its shape but stays tender. It is firmed in barely simmering water, not a rolling boil — too much heat over-coagulates the proteins, driving out water and leaving the blood spongy, holed, and bouncy. The broth is built on lamb bones and meat for body and a packet of more than ten spices (大红袍 Sichuan pepper, fennel, cassia bark, tsaoko, star anise, clove, longan, galangal, pepper) simmered to draw out their aromatics; the strips of blood and the vermicelli are warmed through in it rather than cooked hard. The chili oil is added last so its fragrance stays bright on top, and the dry flatbread, with little gluten development, drinks in broth while holding together.