It was a close thing with United coming back from a goal down, but Wayne Rooney set up the Dutchman twice and he did not fail to move his tally of goals onto six.
Van Persie's second, four minutes into the second half, was the best of the brace, a delicate left-footed finish to Wayne Rooney's cross.
Fergie told reporters after the game: "The second goal was fantastic.
"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."