Spurs were on the brink of utter humiliation in Bern eight days ago, 3-0 down and all at sea on their opponents' plastic pitch.
Having somehow scrambled two away goals to keep the tie alive Harry Redknapp's men proved their class back on grass as Peter Crouch bagged a hat-trick and Jermain Defoe got a goal ahead of his groin operation.
Defoe blatantly controlled the ball with his arm to score his goal, the second of the night, but Spurs were already ahead on away goals and would surely have completed victory anyway.
In truth it could have been much, much worse for the hapless visitors, who had Senad Lulic sent off giving away the penalty that presented Crouch with his hat-trick opportunity.
Young Boys were simply unable to cope with the gangly goalgetter, who earlier scored two unmarked headers to edge the man-of-the-match honours ahead of Gareth Bale, whose four assists surely make him man of the season so far.
After conceding inside four minutes last week, Spurs were in front within five this evening when the visitors left Crouch free to nod home Bale's corner.
Spurs pushed for a second, Aaron Lennon giving Christoph Spycher a particular headache but, unlike last week, the floodgates failed to open, Benoit Assou-Ekotto's piledriver blocked painfully by Ammar Jemal and Tom Huddlestone miscuing a Crouch cross.
All that changed just past the half hour mark, Defoe controlling Bale's pass with his arm before whipping it into the net with his left foot.
The six pairs of officials' eyes on him somehow failed to spot the offence, with Young Boys defender Jemal's furious protests waved away.
Lulic earned a needless yellow card as Young Boys' discipline understandably began to waver but they should have got back in it through Henri Bienvenu, who miscued a great headed chance.
Heurelho Gomes had needed lengthy treatment on a leg injury early in the game and he failed to re-emerge after half-time, Carlo Cudicini making his first appearance since a serious motorcycle accident in November.
The second half continued in the same vein as the first, Bale almost curling a free-kick straight in from wide on the right before Bienvenu almost capitalised on a slip from Michael Dawson.
After that, it was all Spurs, Spycher making a vital clearance with Defoe poised to pounce and King and Crouch both seeing efforts blocked after a corner.
But Crouch made it 3-0 on the hour mark, again rising unchallenged to head in Bale's corner.
The inevitable substitutions followed, including Defoe for Roman Pavyluchenko, who was immediately booked for a poor challenge.
Bale came agonisingly close to the goal his performance deserved before being cut down in the area by Lulic, who saw yellow for a second time.
Up stepped Crouch to complete his hat-trick from the spot and - after Bale was replaced by Niko Kranjcar to a standing ovation - the striker was denied his fourth by a brilliant save from Marco Wolfli.