Tilt skillet and run fork under edge of omelet, then jerk skillet sharply to loosen from bottom of skillet. Spoon half of sour cream mixture onto center of omelet. Fold portion of omelet nearest you just to center. (Allow for portion of omelet to slide up side of skillet.) Turn omelet onto plate, flipping folded portion of omelet over so far side is on bottom, tuck sides under if necessary.