Chop the pak choi into large pieces. The other vegetables should be ped as appropriate and cut into thin matchstick-like slivers.
Put all the prepared vegetables into a medium sized bowl and mix with the marinade. Set aside while you cook the fish.
Cut 3 slices in the skin of the bass fillets and season on both sides. Heat a wok (or heavy based pan) and add the groundnut oil. When it's just smoking, place the fillets in skin down in the oil.
Cook over a medium heat for 4 minutes, shaking the wok about occasionally to avoid sticking, then carefully turn over. Cook for another 45 seconds the remove to a warm plate.
Reheat the wok (adding a little more oil if necessary) then stir-fry all the contents of the bowl for a couple of minutes.
Put the pak choi onto two plates and place one bass fillet on top of each. Pour over the rest of the wok contents and serve immediately.