Prepare the dressing by combining vinegar, mustard, salt, and sugar in a small ceramic bowl. Whisk vigorously until fully incorporated. Slowly drizzle in the oil while whisking continuously until the dressing slightly thickens. Season with pepper to taste.
Place eggs in a saucepan, cover with cold water, and bring to a boil over medium heat while stirring to create a whirlpool to center the yolks. Reduce heat and simmer for 5 minutes. Drain, refresh in cold water, and peel. Set aside.
Place the potatoes in a large saucepan and cover them with cold water. Bring to a boil over high heat and cook for 10 minutes until just tender. Use a slotted spoon to transfer the potatoes to a bowl. Add the beans to the same water and cook for 2 minutes until bright green. Drain the beans, refresh them under cold water, and pat dry with paper towel.
1. Preheat a barbecue grill or chargrill pan to high heat.
2. Lightly coat both sides of the tuna with oil.
3. Cook for 2 to 3 minutes on each side until just cooked.
4. Transfer the tuna to a plate and let it cool slightly.
5. Flake the tuna into 3cm pieces.
In a large bowl, gently mix together potatoes, beans, tuna, tomatoes, and olives. Place lettuce on serving plates, top with potato mixture and anchovies. Cut eggs into quarters, add to salad, drizzle with dressing, season with pepper, and serve.