Start layering the salad by adding the watercress to a serving platter. Then add the green beans, radishes, and eggs.

Remove the skin (if any) from the salmon and use a fork to flake it into small pieces. Add them to the salad. Garnish with a few slices of lemon.

To make the dressing, combine the Dijon mustard, white wine vinegar, and lemon juice in a small bowl or cup. Slowly add in the extra virgin olive oil, whisking continuously, until the dressing has emulsified.