I make this with Shanghai Bok Choy, a smaller Bok Choy than the regular one with light green ribs rather than the white ribs. If you have Bok Choy in a Chinese restaurant, they tend to slice it lengthways and cook the whole thing at once. I decided to cook the ribs and leaves separately and accidentally came up with this recipe because I was distracted after adding the ribs. I found that by overcooking the ribs slightly, they take on an almost buttery flavour, a nice contrast to the freshness of the leaves. I make this with Easy Prep Vegetable Stock (Recipe #247153). One serving of this soup contains quite a lot of protein and is suitable for South Beach or Sure Slim weight loss programmes.