Put the parsley, tarragon, chives, lemon juice, mayonnaise, and sour cream (or Greek yogurt) into a blender and blend until smooth.
Brush the olive oil over the chicken and then sprinkle with the salt and pepper. Cook over medium/high heat for 5-6 minutes on each side, cooking until the inner-most portion of the chicken reaches 165°F. Let it rest for 10 minutes, then slice into bite-sized strips.
Assemble the salad by tossing the mixed greens with the romaine lettuce. Top with the tomatoes, avocado, chicken, pickled onions, egg, bacon, and dressing.
