Combine prosciutto bone or trimmings and oil in a saucepan and cook over low heat for 20 minutes. Remove from heat and set aside to infuse (1-2 hours).
Preheat oven to 150C. Strain oil into a clean saucepan, heat over low heat to 50C. Place fish in a single layer in a deep roasting pan large enough to hold fish snugly. Pour warm oil over fish, ensuring fish is completely covered with oil, cover and cook in oven until fish is just cooked (40-55 minutes). Drain fish with a slotted spoon, then on absorbent paper. Place on a baking tray lined with baking paper.
Meanwhile, for cabbage purée, blanch cabbage leaves in boiling salted water until bright green (2-3 minutes; see cook’s notes p58), refresh, squeeze out excess water and thinly slice. Heat olive oil in a frying pan over medium heat, add onion and garlic and cook, stirring occasionally, until tender (3-5 minutes). Add cabbage and 200ml water and cook, stirring occasionally, until tender (8-10 minutes). Process in a food processor, until smooth, season to taste and keep warm.
For braised cabbage, heat oil in a saucepan over medium heat, add onion and cook, stirring occasionally, until tender (2-3 minutes). Add cabbage, cover and cook, stirring occasionally, until tender
(10 minutes). Season to taste, keep warm.
Increase oven to 200C. Cook prosciutto in a frying pan over medium heat, stir until crisp (8-10 minutes). Scatter over fish then roast in oven until hot (10 minutes). Serve hapuka with puréed and braised cabbage.
This recipe is from the May 2011 issue of Australian Gourmet Traveller.