Night-Blooming Cereus Soup

There is no recorded founding date for this particular soup; it belongs to the broader Cantonese slow-soup (老火汤) tradition of Guangzhou and the surrounding Pearl River Delta, where the humid, sticky climate made a daily pot of long-simmered soup a household institution, summed up in the saying 'better a meal without a dish than a meal without soup.' Its key ingredient, 霸王花 (also called 剑花), is the dried flower of 量天尺 (Hylocereus undatus), a climbing cactus of the same genus that bears the dragon fruit; the plant blooms at night, giving it the English name night-blooming cereus. It is widely grown across Guangdong — Guangzhou, Zhaoqing, Foshan and the Jiangmen area (Taishan, Heshan) are noted producing zones — and harvested mainly from June to September, then split lengthwise, steamed and sun-dried. In Cantonese folk food therapy the dried flower is valued as a cooling, lung-moistening ingredient that eases cough and phlegm, which is why it is paired with pork bone in this 清润 (clearing-and-moistening) soup, especially in dry or hot weather.

A bowl of pale, clean broth, lightly sweet and carrying a soft floral note from the flower. The rehydrated cereus comes apart into tender, slippery strands; the pork bone has given up its sweetness to the broth and the meat by the bones falls away. Seasoned with salt alone — no soy — so the taste stays clear rather than heavy. A few apricot kernels add a faint almond bitterness, the candied date a thread of sweetness, the tangerine peel a clean citrus lift at the back.

Two things carry this soup: drawing flavor out of the bone, and reviving the dried flower. The pork bone is first blanched in cold water brought to a boil to flush out blood and scum that would otherwise cloud and taint the broth, then rinsed before it goes into the pot. Over the long, gentle simmer — Cantonese cooks reckon about three hours — collagen, amino acids and nitrogen-rich extractives leach steadily from the bone into the water; measured protein dissolves only slowly, on the order of 8 to 23 percent, but it is these dissolved extractives, not the meat itself, that give the broth its sweet savor. The dried flower must be soaked back to life first, usually in cold water and rinsed through several changes, because the sun-dried bloom traps grit in its folds; the tough flower base is trimmed off. Cooks skim the surface scum as it rises and lift off floating fat so the finished soup stays clear and clean rather than greasy.