Sun Nong Dan is a specialist in sullungtang, a gentle broth made by boiling beef bones for hours, even days, until the liquid turns a shimmering, pearlescent white that is pretty much the opposite of what French chefs are taught in cooking school. The soup is fatless and softly fragrant, not quite as rich as the soup at fellow specialist Han Bat, but with a sturdy mineral spine and a sensation that you are getting healthier with each sip.
When you first sip sullungtang, you may recoil at its blandness until somebody remembers to tell you that you are supposed to add sea salt and chopped scallions from canisters on the table. A sullungtang restaurant will always have vivid radish pickles on the table; I think it may be a law. If you are so inclined you can dribble some of the tart, spicy brining liquid into the broth, although I never quite think the lovely, beefy version at Sun Nong Dan quite needs it.