Hirschi weathered the storm of a succession of Lambrecht's attacks on the final ascent of the Igls climb, sticking with the Belgian as the front group whittled down to just three riders.
He made his move with just over ten kilometres to go on the descent, immediately establishing a gap that hovered around ten seconds. That advantage was reduced to just six seconds on the final little uphill push into Innsbruck, but the Swiss rider was able to extend his lead on the flat into the finish and ended the race with a 16-second buffer.
"The team did such a great job from the beginning - we were always in the right group and just playing with the others," said Hirschi.
"We knew as a team we were here for the win or a medal, and to get the gold medal, it’s amazing, it's crazy.”
Switzerland certainly pursued an aggressive strategy throughout the race, and once the initial attacks of Szymon Tracz (Poland), Izidor Penko (Slovenia) and Nickolas Zukowsky (Canada) were brought back it was Switzerland who initiated a dangerous move, putting four riders into a seven-man move that went clear on the descent from the Igls climb.
Hirschi was one of four Swiss riders in that group of seven, with the move granting a strategic advantage that forced their rivals onto the backfoot for the rest of the race.
“That was a crucial point, it was not planned like this but we know we can descend well,” Hirschi said afterwards. “We thought the descent was too easy to make any gaps, but with four riders ahead, it was a good situation for us.”
Switzerland were in a good position to cover counterattacks, and did so with Patrick Muller joining Ukraine's Mark Padun off the front, followed by Gino Mader marking Eddie Dunbar's (Ireland) attack.
The Belgians took over the majority of the pace-making on the front of the peloton as the race headed towards the final ascent of the decisive Igls climb, with the intent of getting their WorldTour star Bjorg Lambrecht in a position to attack and take the rainbow jersey.
Lambrecht drove the pace hard to bridge the final gap to Muller and Padun, before attacking again and dropping most of the remaining riders with only two able to follow as they crested the top of the climb.
The leading trio of Hanninen, Hirschi and Lambrecht had a small gap on Padun at the summit before one final plunge back into Innsbruck, but their uneasy alliance soon broke open as Hirschi went clear - again, as he had already done in the earlier seven-man break, on the long descent.
Hirschi made the most of that experience as he eked out every possible advantage on the run into the finish, eventually proving able to hold off Lambrecht and Hanninen to take Switzerland's first medal of the 2018 world championships.
Australia had a limited impact upon the race, with Jai Hindley the closest to maintaining contact with the leaders on the final climb. He finished 11th, 47 seconds behind the race winner.
Robert Stannard finished 17th and Michael Storer was 52nd, while Callum Scotson and Cyrus Monk did not finish.
