Mix together the herbs, garlic and polenta in a shallow bowl. Coat the salmon pieces in the polenta mix, pressing it down firmly.
Put the coated fish on a baking sheet and place in a preheated oven, 200°C (400°F), Gas Mark 6, for 12–15 minutes until cooked through.
Mix together the salsa ingredients in a bowl. Place the salmon on 4 serving plates, top with the salsa and a spoonful of crème fraîche, season with black pepper and serve with a green salad.