Lacey, who joined the Murano brigade in 2011 after previously working with chef-owner Angela Hartnett at York & Albany, was promoted to head chef in 2014.
Her public profile has continued to grow in the past year after she was chosen to serve the winning starter in this year’s series of Great British Menu.
She will continue to cook part-time for the group while working on her own standalone restaurant concept.
Lacey's replacement at Murano will be Oscar Hogado, who joined the Michelin-starred restaurant in 2010 before moving up the ranks to sous chef.
He has since left to take up roles at Fera at Claridges and more recently as head chef at Pitt Cue in the City.
Murano was opened by Harnett and Gordon Ramsay Holdings (GRH) in 2008, but Hartnett bought out the celebrity chef to take sole ownership of the restaurant in 2010.
The Italian fine dining site has held a Michelin star since 2008 and four-AA-rosettes since 2013.