1) Pan-fry the mackerel fillets for 2 minutes on each side.
2) At the same time heat 2 tablespoons of the olive oil and add the garlic and shallots. Cook for 2-3 minutes to soften slightly.
3) In a small bowl, add the tarragon to the rest of the olive oil, sherry vinegar, salt and pepper and mix well. Add the chopped sun blush tomatoes and the chopped fresh tomatoes. Season and mix well.
4) Place the griddle bread onto a plate then top with a fillet of mackerel, spoon over the dressing, serve liberally sprinkled with chopped parsley.