From: Phaidon China Cookbook
Cover the mung beans with cold water and soak for 4 hours. Drain thoroughly.
Cover the dried kelp with cold water and soak for 30 minutes. Clean the kelp, then drain and cut it into 1-inch/2.5-cm sections.
Heat the oil in a saucepan over medium heat, add the ginger, and stir-fry for about 30 seconds until fragrant.
Add the vegetable broth (stock), mung beans, kelp, and winter melon and bring to a boil.
Reduce to medium-low heat and simmer for 2 hours.
Add the salt, adjust the seasoning to taste, and transfer to a tureen to serve.
