The Gullane youngster secured the title with hard-earned one-hole win over Aldeburgh’s Gregor Tait, the second seed, in the 18-hole title decider at Gailes Links.
David Law was just 18 when he won the event for the first time at Royal Troon in 2009.
So, too, were Bob MacIntyre and Sam Locke when they triumphed at Muirfield and Prestwick in 2015 and 2017 respectively.
Connor Graham, who was just 14 at the time, then made it to the semi-finals at Murcar Links last year.
But Mukherjee outshone all those age feats on the Ayrshire coast by going the full distance in Scottish Golf’s flagship event.
‘It feels great, it was a very long week,” he told Scottish Golf at the end of an event that was co-hosted by Gailes Links and neighbour Western Gailes.
‘The courses were in great nick,” added the new champion. “I really enjoyed Western, it’s a world class venue with a great reputation and Glasgow was really good too.
“I’m looking forward to the Boys’ Home Internationals next week at Downfield, but I need some sleep first!’”
Tait held a three-shot lead after ten holes but, helped by back-to-back birdies at the 13th and 14th, Mukherjee levelled the match with four holes to play.
He then got up and down to save par at the short 15th to take the lead for the first time in the final and Tait was unable to convert a ten-foot birdie putt at the last to take it into extra time.
“I didn’t like my chances at the turn but got my energy back and, with some help from my caddie, I was able to turn it round,” said Mukherjee.
“I was pretty tired from quite a long week; I was just trying to stay in it. I think in four of my games I was down this week so I knew if I could win a couple of holes it would put some pressure on Gregor.
“I hit some good shots and holed a good putt on 14. Eighteen had been quite a kind hole for me this week, I hit a good iron shot and a good lag putt to get it done.”