It took Lawrence's second penalty success of the night - his eighth of the season - withthe final kick of the match to clinch victory and a home third round tie with First Division Burnley in the New Year.
Mansfield were excellent value for their half time lead before two goals in three minutes early in the second half from Jermaine McSporran put Wycombe in charge.
But Lawrence levelled on 72 minutes from the spot, and his 14th goal of the campaign sealed a marvellous night for the youngster.
The Mansfield side showed two changes from the one beaten 2-1 at home by Lincoln on , striker Christie dropped to the bench with Disley coming in to play just behind Mendes. And Vaughan's experience and fitness saw him return after a one-game ban in place of Eaton.
The Wycombe side also showed several changes from the first meeting when the sides drew 1-1 at the Causeway Stadium a week last Friday with Williams in goal ahead of Talia, while Wanderers' goalscorer from that first clash, Holligan, and danger man Currie were also on the bench.
Wycombe survived an almighty third minute scramble as Mansfield quickly set out their attacking stall with keeper Williams in all kinds of trouble as the ball bounced around the danger zone.
Stags won their first corner on seven minutes which was cleared back to taker Lawrence. And, as he crossed again, Disley touched the ball well wide of the near post.
Wycombe also saw their first corner successfully defended.
The visitors could only clear a long Hassell throw to the feet of Williamson who controlled the bounce before bundling a half volley well over.
But the breakthrough for the home side came in the 14th minute through another slice of Lawrence magic.
Hassell and Curtis worked the ball to Lawrence in the box. A defender got in the way of his first shot but he looked up and sent a delightful lob over the keeper from just 10 yards out.
Corden soon had a 20 yard shot deflected just wide for another corner as Mansfield took an iron grip in the freezing conditions.
All Wanderers had in reply in the first half hour were a couple of breaks which Stags halted and a couple of crosses which Pilkington gathered.
Disley fed Corden on 34 minutes and his 20-yard shot warmed the hands of Williams who needed two attempts to grab the ball.
Corden came even closer two minutes later. Pilkington punched Wycombe's second corner clear to initiate a break. Two players had shots charged down before Corden's curling effort over Williams saw the keeper just claw the ball into the post. It ran loose to Disley who saw his close range follow-up smothered by the keeper.
Curtis had a shot deflect just over and then blazed another half chance well over as Mansfield continued to dominate.
But Wycombe were almost gifted an equaliser in the one minute of first half stoppage time.
Hassell watched the ball bounce after initially beating Dixon to a clearance, which was all the Wycombe man needed to steal the ball and bear down on goal.
But full marks to Hassell as he chased back and slid in to win the ball as clean as a whistle, as Dixon was about to pull the trigger with any error on timing sure to concede a penalty.
It was Dixon's last contribution as he was replaced by Ryan for the start of the second half.
And Wycombe produced their first shot on goal of the night on 49 minutes as Johnson drilled a firm, low shot at Pilkington from just outside the box.
The visitors had clearly stepped up a gear and Roberts evaded three defenders two minutes later before crashing a rising shot just over Pilkington's fingertips and the bar.
Wycombe's enterprise was rewarded on 56 minutes with an equaliser from McSporran.
Faulconbridge knocked the ball onto him in the box and McSporran turned sharply to drill a low finish just between the keeper's fingers and the near post.
Within three minutes McSporran had turned the game on its head with a second goal.
Simpemba's ball offered him a run on the right of the box and he outpaced Artell before drilling a superb low finish across the keeper and just inside the far post.
Immediately Christie joined the action in place of Disley.
But Stags were on level terms on 72 minutes with Lawrence's second penalty success in four days and seventh spot success of the season.
Christie was quick to pounce on the loose ball as keeper Williams dropped a cross and was then brought down by the hapless keeper.
There was a lengthy delay to the kick being taken while the referee sorted out some wrestling involving Christie and two defenders on the edge of the box. But Lawrence eventually drilled the ball low inside Williams' left hand post.
The action swung from end to end as Christie forced a save from Williams from a low Lawrence cross and then Wanderers broke with McSporran trying to chip Pilkington but not able to get the ball high enough.
Simpemba saw the first yellow card on 77 minutes for bringing down Williamson.
Back came Stags and Christie rolled a defender before shooting into the side netting while Lawrence snatched at another chance and shot well wide as extra-time beckoned.
But there was late drama as Stags snatched victory with the last kick of the match in the third minute of stoppage time.
Williamson was in acres of space in the box, only to be brought down by Johnson. Up stepped ice-cool Lawrence to complete a memorable hat-trick with his eighth penalty success of the season into the same corner, with Williams helpless to reach it and Wanderers helpless to come back as the final whistle immediately blew.
MATCH DETAILS
STAGS: Pilkington, Mendes, Artell, Corden, Vaughan (Dimech 89), Hassell, Williamson, Disley (Christie 60), Lawrence, Curtis, Day. Subs: J. White, Larkin, MacKenzie.
WYCOMBE: Williams, Rogers, Vinnicombe, Thomson, Johnson, Roberts, McSporran, Simpson, Simpemba, Faulconbridge, Dixon (Ryan h/t). Sub: Talia, Bulman, Currie, Holligan.
REFEREE: Paul Taylor of Cheshunt.
ATTENDANCE: 5,512
SCORERS: Mansfield - Lawrence 14, 72 pen, 90 pen. Wycombe - McSporran 56, 59.
CAUTIONS: Wycombe - Simpemba 77 (foul on Williamson); Johnson 90 (foul on Williamson).
MAN OF THE MATCH: Liam Lawrence.