In a food processor or blender, combine all the Tarragon Green Goddess Dressing ingredients. Set aside while you prepare the salad.
For the Little Gem Salad:
Soak the thinly sliced radish in a bowl of ice water while you prepare the rest of the salad.
Place the little gem lettuce on a platter.
Drain the radishes. Scatter the radishes and avocado across the top of the lettuce. Drizzle the salad with the desired amount of green goddess dressing.