Special equipment: mandoline
For the marinade:
Combine all marinade ingredients except for olive oil in the blender. Blend until well combined and slowly drizzle in olive oil. Pour into a bowl and reserve.
In a nonreactive mixing bowl combine the scallops, scallions, onion, peppers, cilantro, and parsley with the marinade. Dress the avocado lightly with some of the leftover marinade. Allow to marinate, covered in the refrigerator, for 2 hours. Place the greens on a large serving plate. Using a slotted spoon, remove the ceviche and place on top of the greens leaving some of the marinade behind. Place the avocado over the greens. Fold the sliced radishes into the ceviche. Drizzle a little of the marinade over the plate and serve.