Place the garlic in a saucepan of salted water and bring to the boil. Immediately refresh in cold water and repeat until the garlic is tender.
Dry the fish with paper towels and season with sea salt.
Heat the olive oil and half the butter in a heavy-based saucepan over medium heat until hot. Add the fish pieces skin side down and cook for 5 minutes or until the skin is nice and crisp. Turn the fish over and add the garlic. Cook for a further 3 minutes until the fish is about three-quarters done.
Remove the fish and keep it warm; the residual heat will continue to cook the fish as it rests.
Add the vinegar to the pan and scrape the bottom and sides with a wooden spoon to deglaze. Then add the tomatoes, olives and a little sea salt. Cook for 5 minutes then add the remaining butter and whisk until it melts and forms a sauce. Add the parsley and a little freshly ground pepper, then check the seasoning to finish.
Pour a little sauce on each plate and place fish on top. Serve immediately.
We use thick steaks from larger fish - about 3kg to 5kg. If you use thin fillets, adjust the cooking time downwards to suit.
Make sure the fish is a little undercooked in the kitchen so it's perfect by the time it gets to the table.