“Wash the sheep’s stomach clean, boil it until soft, slice it into thin strips, and braise it in its boiling liquid. Pepper and vinegar can be added when braising the stomach. The Northerners have a technique for making stir-fried sheep’s stomach, but Southerners that prepare it fail to get the desired crisp texture. Prefect Qian Yusha makes a very good pan-fried mutton. I will soon learn how to prepare it from him.”
Judging from the way this sheep’s stomach geng or “thick soup” is made, it’s likely a Southern Chinese preparation. Indeed, Yuan Mei kinda indicates this in the third sentence, basically saying that Northern Chinese prepare their stomach “crisp” while Southern Chinese are only good at making it soft. The fact that sheep stomach here is similarly prepared to the Southern Chinese pork stomach recipe from a previous chapter, is probably also a good indication that it’s Southern.
As for that recipe from Qian Yusha, it seems Yuan Mei never got to writing about it, not to mention also that an entire section on pan-fried mutton (鍋燒羊肉) appears to be missing in the Suiyuan Shidan.