Tottenham took apart Marcelo Bielsa's men, responding to their 1-0 defeat against Burnley last time out in fine style, and did so thanks to their key men yet again.
Kane and Son have now moved clear of Didier Drogba and Frank Lampard's previous record of 36 goals scored and assisted between them, and did so in stunning fashion.
Matt Doherty and Dejan Kulusevski as good as ended the game by putting Spurs 2-0 up within the first 15 minutes, but Kane and Son still managed to steal the show.
The England captain made the score 3-0 before half-time with an exquisite tight-angled finish from a Pierre Hojbjerg cross, but arguably bettered his goal with a later assist.
Kane picked the ball up in his own half with five minutes left to play and guided a pinpoint curling ball over Leeds' midfield and back-four for Son to collect and dispatch.
Son's finish past Illan Meslier was excellent, but Kane's performance came in for extra praise from talkSPORT commentator and former player Micky Gray.
"It's that man again, Harry Kane, who provides this time - he's been sensational today," Gray said, speaking live from Elland Road.
"His build-up play, his hold-up play, the goal he got for himself…
"I mean, he's in his own half! He sees the run of Son who gets in between the two centre-halves, Kane has lifted his head and has found him the most perfect pass that just takes everybody out of play.
"What a goal and what a way to top off this performance against Leeds. Harry Kane and Son have been first class."
Kane and Son have played together since the Korean moved to north London from Bayer Leverkusen in 2015, featuring in 257 games as a pair.
That total is less than Drogba and Lampard's 304 games together with Chelsea, showing just how productive they've been.
"It's a big honour," Son said after the match as he spoke alongside his strike partner.
"To get the record is fantastic, but the three points were [more] important because the result [against Burnley] was not the best or what we wanted."
On their partnership, Kane added: "We've being playing with each now for a long long time, we just understand each others games well.
"When I drop deep, Sonny knows where to run and hopefully I'm able to put him in - you saw that from the last goal.
"We enjoy playing together but the most important thing is the team and it was a fantastic display from everyone."