Prepare the smoker for barbecuing, bringing the temperature to 200°F to 220°F.
Mix the onion, shallots, and white portions of the scallions with the oil and pour into a shallow, smoke-proof dish or shallow tray made of doubled heavy-duty foil. Place in the smoker and smoke until the onions are tender, 50 to 60 minutes. Mix with the sour cream, Worcestershire sa