– 6 oz. (170 g) Guilin rice noodles, dry – 4 tablespoons melted unsalted butter – 6 slices peeled ginger – 1 cup canned chicken broth – 2 cups water – 1/2 cup evaporated milk – 2 lb. (1 kg) crab, cleaned and cut into pieces – 5 baby bok choy, cut lengthwise into halves – 1 tablespoon rice wine – 1/2 tablespoon fish sauce, or to taste or salt to taste – 3 dashes white pepper – 1 stalk scallion, cut into 1-inch lengths