Salade Niçoise

1. Start by cooking the potatoes, green beans, and eggs.
2. For the dressing, whisk together vinegar, lemon juice, salt, and sugar until the sugar dissolves.
Stir in the mustard. While whisking, gradually add olive oil drop by drop.
3. Cut the tomatoes into six pieces and quarter the eggs.
4. Mix potatoes, green beans, capers, tomatoes, olives, tuna, anchovies, and herbs together.
5. Gently fold the dressing through the salad.
6. Line 4 plates with lettuce leaves. Divide the salad over them. Garnish with the eggs.