Wash the fish steaks and pat dry with kitchen towels. Rub with pepper on both sides, but do not salt as it would draw out the juices. Marinate for an hour in the wine and vinegar.
Meanwhile, peel the garlic cloves, cut in half and remove any green shoots in the centre that can taste bitter. Cut each half in four, so you end up with 16 slivers.
Heat a heavy ridged griddle pan on the hob. Remove the fish from the marinade, pat dry and make 4 well distributed small incisions in each steak with a sharp knife. Wrap a mint leaf round a garlic sliver and insert one into each of the incisions.
Brush one side of each fish steak with olive oil, place oiled side down on the griddle, turn down the heat and cook for 3 minutes. Brush the second side with oil while it is on the griddle, then turn the fish over. Turn the heat up for one minute only, then turn it down again and cook the second side for another minute or two. When the fish is cooked it should be moist inside, with white flesh that flakes easily.
Take the fish off the heat and season both sides, drizzle with olive oil, scatter with the herbs and serve with the lemons to squeeze over.