Preheat the oven to 200 degrees F. Heat the oil in a non-stick skillet over medium-high heat. Season the scallops with salt and pepper and then cook 1-2 minutes on each side, or until just barely cooked through. Divide and arrange scallops on 2 plates and keep warm in the oven. Add shallots and garlic to the skillet and cook 1 minute. Add sherry and reduce it by a half. Remove from heat, and then slowly whisk in the butter, a few cubes at a time, adding the next cube just after the first has melted. Whisk in tarragon or parsley. Spoon sauce over the top of the scallops and serve immediately.