“Take some cooked mutton and cut it into small pieces the size of dice. Braise the meat in chicken broth. Add diced bamboo shoots, diced shitake mushrooms, and diced mountain yam then braise until done.”
I love geng. The thick texture, rich umami flavours, and the delicateness of its broth makes geng one of the most comforting things one can have for dinner during a cold autumn evening or frigid winter night. It’s a silk comforter in soup form.
The thick texture of geng is conferred through the addition of a starch, such as potato, corn, or arrowroot starch. These starches give the otherwise texture-less broth a silky body, which stays in the mouth and feels somehow more “weighty”. They make the liquid broth much more substantial, while maintaining the broth’s clarity. In this regard, all thick textured Chinese soups are technically geng since they consists of ingredients in clear broth given substance through added starch. While this recipe does not call for starch explicitly, it may simply be that it’s assumed to be added or more likely that mountain yam (known to be quite mucilaginous) provides the thickening during braising.
Geng is sometimes translated as “stew” or “thick soup”, but I feel both are inadequate since they allude to the stogy opaqueness of dishes thickened by flour and roux. The clear delicateness of a geng’s thickened broth is mostly lost in such translations. Just as very few refer to tofu as “bead curd”, and sushi as “seaweed roll”, geng should not be called anything but “geng”.
That aside, it is interesting to note that mutton geng is now rarely called “yang geng” (羊羹) but rather “yang rou geng” (羊肉羹, lit. sheep meat geng). The addition rou (肉, meat) is required since when someone uses “羊羹” they are usually talking about a Japanese Yōkan, a sugary bean jelly that is largely unrelated to mutton geng except for its culinary ancestry. A summary of how this came about is as follows: A mutton geng made with gelatinous broth becomes an aspic when chilled and was eaten this form in Ancient China. Then Medieval Chinese vegetarians Buddhists who moved from China to Japan replaced the meat with bean pastes and starch. Then the medieval Japanese replaced starch with agar and added sugar into the mix, which turned everything super sweet. And that my friends, was how “羊羹” went from a savoury meaty soup to become a sweet sugary block of firm bean jelly.