But with Birkenhead seeming certain to make Smith's brace a match-winning one, Waitakere had other ideas. First, a lively Dylan Manickum pulled back a goal in the 86th minute, before a questionable penalty allowed Keegan Linderboom to fire in an equaliser in the final minute of normal time.
There, Birkenhead suffered another blow when Ryan Cain was sent off for a second yellow to cap an occasionally spiteful match, but the reduction in numbers eventually proved no impediment as Galbraith sent the sizeable Birkenhead contingent into raptures.
Meanwhile, Forrest Hill Milford United made history of their own in the Women's Knockout Cup final, taking their first title after defeating Glenfield Rovers in a penalty shootout.
Glenfield had seized an early lead through Liz Milne but a long-range strike from Forrest Hill Milford captain Tessa Berger sent the game into extra time. Milne soon struck a second to leave her side on the verge of glory, only for Emma Rolston to again lock up it up with 10 minutes left in the extra period.
And in a shootout that saw seven spot kicks missed, Tayla Christensen eventually stepped up and coolly slotted home the decisive penalty.
Birkenhead United 3 (Jarrod Smith 23, 38, Ethan Galbraith 111)
Waitakere City 2 (Dylan Manickum 86, Keegan Linderboom 89)
Halfitme: 2-0
Forrest Hill Milford United 2 (Tessa Berger 52, Emma Rolston 110)
Glenfield Rovers 2 (Liz Milne 17, 102)
Halftime: 1-0
Fulltime: 2-2
Forrest Hill wins 4-3 on penalties