Peel off any wilted or discolored leaves from the outside of the lettuce. Trim the core even with the bottom of the lettuce and cut the lettuce into quarters through the core. If the quarters look too big for a single serving, either cut them in half or trim them to whatever size you feel is a good serving.
Combine the sour cream, yogurt, mayonnaise, garlic, vinegar, and chives in a bowl until well mixed. Season with salt and pepper. Cover and refrigerate until ready to use.
To serve, set the wedge of iceberg in the center of a salad plate, spoon the dressing over and dash it with a good pinch of chives.