What vegetable originating near the Beijing region of China is used in Haejang-guk?
Haejang-guk: Haejang-guk (해장국 ) or hangover soup refers to all kinds of "guk" or soup eaten as a hangover cure in Korean cuisine. Haejang-guk:  It usually consists of dried Napa cabbage, vegetables and meat in a hearty beef broth. Napa cabbage: Napa or nappa cabbage ("Brassica rapa" subsp. Napa cabbage:  "pekinensis" or "Brassica rapa" Pekinensis Group) is a type of Chinese cabbage originating near the Beijing region of China, and is widely used in East Asian cuisine.
Napa cabbage