Cream of lettuce soup, sea bass with potatoes and watercress sauce

Name: Cream of lettuce soup, sea bass with potatoes and watercress sauce
Prep time: 10 min
Cook time: 30 min
Total time: 30 min
Yield: 2 portions
Ingredients: 30 - 40 g watercress; 5 - 10 g lemon juice; 2 tsp fine salt; 1 tsp ground white pepper; 50 g extra virgin olive oil; 500 g water; 500 g potatoes; 10 - 12 green lettuce leaves; 500 g sea bass