The forward's treble completed a 3-1 victory (6-3 on aggregate) to avenge defeat in two finals by their rivals last season.
The defeat means the Steelers' astonishing run of success - they had won the last five domestic trophies - was ended as Nottingham reached next month's final at Sheffield Arena for the third year running. Sheffield now play Ayr Scottish Eagles who beat Basingstoke Bison 9-4 (aggregate 9-6).
Laxdal sealed Panthers' triumph when he slid the puck home with just 16 seconds left after Sheffield had withdrawn their net-minder, Piero Greco, in a vain attempt to salvage the game.
Nottingham had been given the perfect start by Laxdal when he fired home an early goal before Steelers' Tony Hand equalised soon afterwards from the narrowest of angles.
From then the visitors found Panthers' keeper, Trevor Robins, in magnificent form. In the second period Nottingham regained the lead when Laxdal scored from close range after receiving a pass from Marty Dallman.
Sheffield piled on the pressure near the end but could not make a breakthrough.Reuse content