Jennifer Aniston went all out for Brad Pitt's milestone birthday back when they were married in '03 -- gifting him a surprise personal visit from Chef Jamie Oliver as his big gift.
The British culinary whiz recently dished on once being flown out to cook for Brad’s 40th birthday party ... explaining how he initially hung up on the "Friends" star 3 different times, thinking it was a prank ... before she finally broke through via their reps.
Oliver says he usually skips cooking for celebs -- but makes exceptions for folks he admires. So when Jen asked him to surprise Brad -- who was apparently a big fan of Jamie's 'Naked Chef' show at the time -- he jumped at the opportunity.
Jamie says everything went off without a hitch -- and Oliver has nothing but love for the now-exes ... who he says he's stayed in touch with. He says he even saw Jen recently, and had nothing but kind words for her.
Oliver’s wife first spoke about this dinner back in 2014 ... joking about how awkward it was for her to make small-talk with the A-list crowd ... which also included Jen’s "Friends" costar Courteney Cox.
Of course, despite the nice gesture -- Jen and Brad’s marriage didn’t last ... they split up two years later, and the rest is history.