Stem’s restaurant manager Emma Underwood also left earlier this year, and will soon launch Robin Gill's Darby’s as general manager.
No official statement has been released regarding Ashton-Booth’s departure, but in a statement on his Instagram account the chef said: “I am proud of everything we have achieved here [at Stem], and would like to thank all the suppliers, staff and guests for the last 12 months.
“I have been blessed with the most incredible team of hard-working chefs, and couldn’t have done it without them.”
Going forward, Ashton-Booth says he has "a few personal things lined up".
Before taking the reins of Stem’s kitchen, Ashton-Booth worked as head chef at Jarvis’ debut restaurant Anglo in Farringdon, which was named Best Newcomer in the 2016 Observer Food Monthly Awards and has appeared within Restaurant Magazine’s list of the top 100 restaurants in the UK.
Ashton-Booth also previously oversaw the kitchen at Tom Sellers' Restaurant Story as head chef.
Stem launched in January 2018 as part of a regeneration of the area by landlord The Crown Estate. It was Jarvis’ second restaurant to open in the area around London Oxford Street and Regent Street, following on from the opening of Neo Bistro on Woodstock Street, which is now closed.