To make the broth, put the stock, rice wine or sherry, soy sauce, ginger, garlic and lemon into a wok or wide non-corrosive saucepan and bring to the boil.
Measure the thickness of the fish at its thickest point. Reduce the heat under the broth and slip the fish in, making sure it is completely submerged. If necessary, add a little more stock or water. Poach the fish for 10 minutes for every 2.5 cm (1 in) of thickness, or until it turns opaque and the flesh flakes easily.
Carefully lift the fish from the broth, remove the skins and divide the flesh between four shallow bowls. Cover and keep them warm.
Return the broth to the boil and add the broccoli, spring onions, Chinese leaves and carrots in this order at 30 second intervals and cook for a total of 2-3 minutes, or until the vegetables are tender but still crisp. Remove with a slotted spoon and divide them between the bowls with the fish.
Boil the broth for 30 seconds. Remove the ginger and lemon slices and stir in the sesame oil. Pour the broth over the fish and vegetables and serve.