Place a saucepan over a medium heat and add two tablespoons of olive oil. Stir in the chopped celery, shallots, and garlic. Leave to simmer for about three minutes. Then stir in the chopped tomatoes and white wine – allow to simmer for about five minutes. Next stir in the fish stock, olives and sorrel. Reduce the heat to low, season with sea salt and freshly ground black pepper and simmer for 20 minutes.
While the broth is simmering cook the seabass. Place a griddle pan, or frying pan over a medium heat. Brush the fish with the two tablespoons of olive oil and season with sea salt and freshly ground black pepper. Place the fish on the hot pan and cook for five minutes on each side.
To serve, spoon the broth onto warmed plates and place the cooked fish on top, followed by a garnish of sorel leaves and lemon wedges.