Cooking guidelines from defrosted:

Pan-fry:

Rinse the fish quickly under cold running water then pat dry with kitchen paper.
Lightly coat in plain flour. Heat a large frying pan to a moderate heat and add a little oil.
When the oil is heated carefully add the fish and fry for 3-4 min, turn carefully and fry for a further 3- 4 minutes, just before it's fully cooked add some cubes of unsalted butter and baste the fish with the foaming butter.
Season with salt and pepper and finish with a squeeze of fresh lemon juice.
Remove the fish from the pan and allow to rest for 1-2 minutes before serving.
To serve remove the top fillets by sliding a palette knife under and lifting them off the bones. Once all the flesh is removed, lift the bones from the tail end to give access the two bottom fillets.
Trap the lateral bones (which run all around the outside edge of the fish and into the fillets) with a knife and drag them away.
Arrange the pieces onto preheated plates and sprinkle with the pan juices.

Oven bake:

Rinse the fish quickly under cold running water then pat dry with kitchen paper.
Using a sharp knife cut 2 incisions into the thickest part of the top fillets. This will allow the fish to cook evenly.
Preheat the oven to 200°C Fan / gas 6. Brush a large baking tray with a little oil and heat, once hot carefully place the fish skin side down into the tray, brush lightly with melted butter.
Season the fish with salt and pepper. And place in the middle of the oven and cook for approx. 6 - 7 minutes or until the flesh has turned opaque and lifts from the bone, test at the thickest part of the fish.
Half way through the cook brush the fish heavily with softened butter.
Remove the fish from the oven and allow to rest for 1-2 minutes before serving.
To serve remove the top fillets by sliding a palette knife under and lifting them off the bones.
Once all the flesh is removed, lift the bones from the tail end to give access the two bottom fillets.
Trap the lateral bones (which run all around the outside edge of the fish and into the fillets) with a knife and drag them away. Arrange the pieces onto preheated plates and sprinkle with the pan juices.