One of Warren Buffett’s youngest protégés is parting ways with Berkshire Hathaway — to start a rival company.

Tracy Britt Cool — who started at Berkshire in 2009 when she was just 25 — is launching an investment firm that will own smaller companies — just like the one she has helped the Oracle of Omaha run for the last decade.

“There are companies that I think there’s a lot of value in helping them get to the next level, but they’re too small for Berkshire,” she told The Wall Street Journal in announcing her spring departure.

Buffett added: “Anything I’ve assigned her she’s done a first-class job on.”

Still, Buffett fans were scratching their heads over the departure as Berkshire is known for hanging on to its staff for life.

“I’m very surprised she is leaving,” said Dr. David Kass, a University of Maryland professor who blogs about Warren Buffett. “She’s been there about 10 years and there is very little turnover at headquarters,” Kass said.

At last year’s annual meeting, Buffett showed a picture of his executive team from 2018 followed by a photo of the team the prior year to illustrate how it never changes, Kass said.

But Cool was also a key player in one of the Oracle’s worst investments: food giant Kraft Heinz. What’s more, the only Berkshire company where she has been named CEO is suffering sagging sales.

Since Cool and Greg Abel — chairman and CEO of Berkshire Hathaway Energy — joined the board of Kraft Heinz in 2015, the company’s stock has lost 60 percent of its value and closed at only $28.41 a share on Wednesday.

Berkshire owns 27 percent of Kraft Heinz, which has been losing money since drastic cost-cutting measures — spearheaded by Buffett’s partner in Kraft, 3G Capital — have left the business without the money it needs to expand amid slowing sales and increased competition.

“[Cool] was his eyes and ears,” a businessman who recently talked with Cool said of her responsibility to Buffett. “She missed one on Kraft Heinz,” the source added.

Cool was named CEO of Pampered Chef, which enlists home chefs to help sell its cookware, in 2014. The company’s revenue has fallen from $320 million in 2015 to $280 million in 2018, according to Direct Selling News.

Buffett told the Journal that Pampered Chef’s second quarter revenue was up 19 percent, but failed to mention the revenue losses since Cool — who joined the company as a financial assistant straight from Harvard — has taken the helm.

Over at Berkshire’s Benjamin-Moore, however, revenue has been rising. Cool, who is the paint seller’s chair, swung the ax there in 2013, firing many sales reps despite Buffett’s public pledge to rebuild the 130-year-old brand’s network of mom-and-pop dealers, The Post reported at the time.

She is also a director of Blue Apron, which reported a 28 percent jump in revenue earlier this year, despite a decline in customers.

Berkshire and Cool did not return calls.