Pat the fish dry and rub extra sea salt over the skin. Heat the olive oil and cook the fish fillets, skin side down on a very high heat, for 3 minutes or until crisp. Turn the fish over and cook 2 minutes more. Meanwhile, rinse the mixed watercress and spinach and place in a large saucepan with a tightly fitting lid for 2 minutes, or just until wilted. Pour into a large bowl and dress with vinaigrette. When the potatoes are cooked and sliced, add a little virgin olive oil and salt to taste while the potatoes are still warm. To serve, place 3 or 4 potatoes on each plate, top with a mound of wilted greens and place 2 fish pieces on each plate. Top with pesto or sundried tomato paste if desired. Per serving: 0 Calories (kcal); 0g Total Fat; (0% calories from fat); 0g Protein; 0g Carbohydrate; 0mg Cholesterol; 22560mg Sodium Food Exchanges: 0 Grain(Starch); 0 Lean Meat; 0 Vegetable; 0 Fruit; 0 Fat; 0 Other Carbohydrates Converted by MM_Buster v2.0n.