Preheat the oven to 350°F and lightly butter a deep ovenproof dish. Place the garlic, carrots, tomatoes, onions, herbs, wine, salt and pepper in a medium saucepan, cover and cook over a medium heat for 15 minutes, stirring from time to time. Remove the bay leaf.
Meanwhile, bring a large pan of lightly salted water to the boil, add the sweet potato slices and cook for about 10 minutes.
Drain the potato slices and place in the bottom of the prepared dish. Add the vegetables then top with the fish. Bake for 30 minutes. Serve hot.