Blanch the pak choi in boiling salted water for 2-3 minutes, drain and squeeze out any excess water. Melt half of the butter in a frying pan and sauté the pak choi for a few minutes. Arrange on a warm plate.
Lightly dust the sea bass with curry powder. Heat the remaining butter in the frying pan and fry the fish skin-side down for 3-4 minutes, then turn over and fry for another minute or until cooked through. Place on top of the pak choi.
For the chilli dressing, blend all of the dressing ingredients together in a mini food processor. Spoon around the pak choi and fish.
For the onion salad, toss the onion, oil and parsley together in a bowl and serve alongside with the sea bass.