Heat the oil in a large stainless-steel saucepan and, when hot, gently sauté the onion rings until translucent. Add the ginger, garlic, Hinds Spices Mild & Spicy Curry Powder, Hinds Spices Turmeric, bay leaves, whole allspice and cumin and fry gently for a few minutes, or until fragrant.
Add the vinegar and sugar and stir until the sugar has dissolved. Simmer for 20 minutes. Dust the fish with the seasoned flour and pat off any excess.
Heat theremaining oil in a heavy-based frying pan and, when hot, fry the fish untilgolden but still succulent.
Place a layer offish in a deep glass dish and pour a little of the hot sauce over, to cover. Continue layering the fish and sauce until all the fish is covered. Cool, and then chill until ready to serve.