You can prepare all ingredients that require cooking up to a day ahead. Cook the baby potatoes unpeeled, then cool and cut in half. I prefer cooking my potatoes in Instant Pot for 5 minutes at High Pressure but you can simply boil them, which will take 10 minutes.
For soft boiled eggs, put the eggs in cold water in a saucepan, bring to a boil, then turn the heat off and let the eggs sit in the water for 5 minutes. Afterwards, transfer the eggs to ice cold water until completely cool, then peel. Green beans will take 5 minutes to cook after the water comes to a boil. Take off the heat and plunge into ice cold water to stop the beans from cooking immediately to preserve the firm texture and the vibrant green colour.
Next make the salad dressing by combining the anchovies, a clove of garlic, white wine vinegar, olive oil and salt in a small blender, process till smooth, then stir in chopped chives and parsley. Alternatively, you can chop the anchovies very finely, then mash them with the back of a spoon into a paste, followed by pressed garlic and the rest of the dressing ingredients. Mix everything together until you well combined.
To assemble the salad, quarter the head of the lettuce lengthwise and arrange the wedges on a large platter. Top with halved baby potatoes, chunks of canned tuna, soft boiled eggs, which were cut in half, green beans, olives and quartered tomatoes. Sprinkle with some salt, then drizzle with the salad dressing. Serve immediately.