Place the potatoes in a small pot and cover with water. Bring to a boil and cook for 8 minutes. Drain and set aside to cool then cut in half and sprinkle with 2 tablespoons champagne vinegar, salt and pepper.
Fill a medium bowl with ice water and set aside. Heat 2 inches of water in a skillet to boiling, season with salt and blanch the haricots verts until just tender 1-2 minutes, remove from the boiling water and place in the ice bath to stop them from cooking and maintain the color.
Toss the cut tomatoes with a little olive oil and salt and pepper. Combine all vinaigrette ingredients into a bowl and whisk to combine, or place into a mason jar and shake.
Dry the salmon filets with a paper towel and sprinkle the salmon with salt and pepper. Heat a nonstick pan over high heat. Add the oil to the hot pan and cook the salmon flesh side down first 2-3 minutes until there’s a golden crust. Flip the salmon and continue to cook 2-3 minutes more. Remove the salmon and serve flaked over the salad.
To build the salad, divide the lettuces between 4 plates, top each with a pile of potatoes, haricots verts, cherry tomatoes, sliced radishes, boiled eggs and olives. Top with flaked salmon and drizzle heavily with the caper vinaigrette