Season the prawns and scallops with salt and freshly ground white pepper.
Heat 1 tablespoon of the oil in a wok over a high heat until the oil starts to shimmer. Add the prawns and stir-fry for 2 minutes until they begin to colour, then remove using a slotted spoon and set aside. Add another tablespoon of the oil to the wok and, once it is hot, stir-fry the scallops for 1 minute on each side. Remove using a slotted spoon and set aside.
Heat the remaining oil in the wok. Stir in the ginger, garlic and asparagus and stir-fry for 1 minute, then add the rice wine, vinegar, soy sauce, sugar and water and bring to the boil. Return the prawns and scallops to the wok and stir-fry until they are cooked and the asparagus is just tender. Add the sesame oil and give everything a good stir, then serve.