Preparation: Wash & soak Chinese mushrooms & dried shrimp in warm water for 1 hour until soft. Mince shrimp. Remove hard stem from mushrooms. Wash & thinly slice mustard green.
Separate cabbage leaves; blanch in salted boiling water for 30 seconds; drain; slice into 2" sections. In a bowl, combine stock, salt, sherry, sugar & soy sauce; reserve. Render chicken fat in small saucepan at medium heat; discard pieces of fat; keep oil hot.
Braising: Heat peanut oil in wok until hot but not smoking. Stir-fry mushrooms, shrimp & mustard green for 15 seconds. Add cabbage; stir-fry for 1 minute. Add stock mixture; bring to boil. Reduce heat, cover wok, & simmer for 10 minutes, reducing liquid by half; add more stock if needed.
Turn up heat; add enough cornstarch paste to make light sauce. Swirl in hot chicken oil. Serve.
Note: Cabbage leaves should become transparent, but avoid overcooking; they should be soft but not wilted.