United were on the verge of a deflating setback at Molineux on 1 February, after late goals from Max Kilman and Pedro Neto had eroded our 3-1 advantage.
With 96 minutes already having passed, it seemed certain the Reds would have to settle for one point, rather than three, when Omari Forson funnelled the ball to Mainoo, about 25 yards from goal.
Taking control of the ball in the inside-left channel, there seemed little on for the youngster, who was making just his ninth appearance in the English top flight.
What came next has already entered United folklore: Mainoo danced past one defender, nutmegged another, used Forson's run to open up a shooting angle, and then used one final Wolves player as a guide to curl the ball home with languid ease.