1.Preheat oven to 220°C/200°C fan-forced.
2.Boil, steam or microwave potato until tender; drain. Divide potato, garlic and thyme among two oiled large shallow oven trays; drizzle with half the oil. Roast potatoes, in oven, 20 minutes.
3.Meanwhile, pat fish dry, inside and out, with absorbent paper. Score fish three times both sides. Place orange slices inside fish cavities
4.Remove trays from oven; set aside garlic cloves. Top potato mixture with fish; roast about 20 minutes or until fish are cooked.
5.Meanwhile, squeeze garlic from bulbs; chop finely. Combine garlic, wine, rind, juice, sugar and chilli in small saucepan; simmer, uncovered, until reduced by half. Stir in remaining oil.
6.Divide potato among serving plates; top with fish then sprinkle with parsley and drizzle with warm orange dressing.