Combine all ingredients except olive oil in a food processor or blender. Slowly stream in olive oil while processing until smooth. Taste then adjust salt and pepper if necessary then refrigerate for at least a couple of hours and up to 3 days to let the flavors meld.
For the Salad:
Divide lettuce between four plates then divide toppings between plates. Drizzle with Tarragon Vinaigrette then serve.
Notes
Estimated nutritional information includes the entire vinaigrette recipe.