Van Persie's second, four minutes after half-time, was the pick, a delicate left-footed finish to Wayne Rooney's cross.
It took Van Persie onto six goals for United and left Ferguson, a former striker himself, purring.
"The second goal was fantastic," he said.
"It was a great ball from Wayne.
"I thought he had hit it too far in front of him. But the speed to get to the ball and his deftness of touch were fantastic."