A penalty try and three Morgan Parra penalties actually had the French ahead 16-13 at the start of the second half.
But tries from Benn Robinson and Will Genia in the 48th and 51st minutes put Australia in control, before Mitchell claimed a quickfire hat-trick and James O'Connor added a try of his own to complete a personal haul of 29 points.
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Hide AdThe 20-year-old winger has now scored a total of 119 points in test matches to become the second youngest player after England's Jonny Wilkinson to reach 100 points.
France were completely outplayed in very department except for the scrum but even the Wallabies' disastrous set piece became largely irrelevant in the incredible second half and the home crowd made their feelings clear as the French team left the field to a chorus of boos.