Season the fish with salt and freshly ground black pepper and rub the oil into the flesh. Heat a pan until smoking and place the fish, skin-side down, in the pan for 2-3 minutes, or until golden-brown and crisp. Turn the fish over and continue to cook for 1-2 minutes, or until golden-brown all over and cooked through. Remove from the pan and leave to rest on a warm plate.
In the same pan, fry the onion, ginger and broccoli for 3-4 minutes, then stir in the mustard and cream and cook for 3-4 minutes, or until the broccoli is tender.
To serve, place the broccoli on a serving plate and arrange the sea bass fillet on top. Garnish with the sliced red chilli.