Min Woo Lee, nicknamed The Chef, had the world's leading golfers eating out of his hand with an eight-under-par 62 on Friday (AEST) at East Lake.
It was good enough to lead the exclusive field at the season-ending tournament in Atlanta, with nearest challengers Viktor Hovland, Collin Morikawa and Chris Gotterup two behind.
World No.1 Scottie Scheffler is among a four-player group at five under, while Australian Adam Scott (66) is one further back.
Lee made an elecrifying start in his Tour Championship debut, which no-one saw coming, after two lowly finishes - tied 55th and 47th - to begin the FedEx Cup playoffs.
"Very average two weeks the last two weeks. It was probably the saddest I've been on the golf course, which is not good," Lee said.
"We're really lucky to be out here and play some good golf to get into the playoffs. It just felt so hard."
With runner-up finishes this year at Pebble Beach and the Scottish Open, Lee was a lock to be among the top 30 players who get a shot at the FedEx Cup, the $10 million ($A14m) prize and a five-year exemption on the PGA Tour.
Lee coined his nickname after his popular catch phrase "let him cook" went viral.
He had the right recipe on Friday, taking advantage of the rain-softened course to post eight birdies - four on each nine including the last - to match his career-low best total on the Tour.
Former world No.1 and 2013 Masters champion Scott also hit his straps.
The Tour Championship is special to Scott, who won the tournament back in 2006.
The Queenslander has been ultra-consistent since, with a consecutive major championship streak of 101 straight starts that makes him only the second player in the history of professional golf to achieve the feat.
Scott produced five birdies with a lone bogey, leaving him tied ninth.
Scheffler started his day with a six-foot par putt and never came close to another bogey in his round of 65.
He is No.1 in the FedEx Cup and picked up a $23 million bonus last week, but that doesn't matter at East Lake as under the current format any of the 30 players who win the Tour Championship are deemed to be the FedEx Cup champion.
Rory McIlroy, the only three-time FedEx Cup champion, opened with a 68.
7°C