Combine the pepper, five-spice powder, salt and cayenne pepper in a small bowl. Brush the salmon with a little of the oil and dust with the spice coating. Cook the fish in a preheated frying pan for 4 minutes, then turn and cook for a further 2–3 minutes until the fish is just cooked through. Transfer to a plate, cover with foil and leave to rest for 5 minutes.
Meanwhile, heat the remaining oil in a wok, add the choi sum or pak choi and stir-fry for 2 minutes, then add the garlic and stir-fry for a further 1 minute. Add the shao hsing or sherry, stock, soy sauce and sesame oil and cook for a further 2 minutes until the greens are tender.
Serve the salmon and greens with boiled rice.