Bosi confirmed in an Instagram post that Garrett, whose career has seen him cook under the likes of Nico Ladenis, Bruno Loubet and Chris Galvin, would be working alongside group executive chef Claudio Illuminati and executive pastry chef Jamie Warley.
“Lucy Bosi and I have known André for a long time and followed his career,” he said.
“French culinary expertise will be a massive asset to our business, and [we] look forward to be working together.”
It comes after Garrett quietly stepped away from the Corinthia in Whitehall in May after more than six years overseeing the hotel’s food and beverage.
Prior to that Garrett, whose decorated career saw him win the Roux Scholarship in 2002 and compete in the Bocuse d’Or in 2007, spent just over five years as executive chef at Cliveden House in Berkshire.
The chef will begin his new role helming the kitchen at the recently launched Josephine Bouchon in Marylebone, sister restaurant to Josephine Bouchon in Chelsea, alongside head chef Connor Jack Twomey.
Bosi’s group also includes his eponymous Bibendum restaurant in Chelsea and Brooklands by Claude Bosi at The Peninsula London, which both hold two Michelin stars.