The Garden Room, in Stoke Place hotel, in Stoke Green, Stoke Poges, Bucks, has achieved 'outstanding' status following several visits from undercover inspectors.
The cuisine, overall experience, quality of wine list and outstanding level of customer service were singled out for praise by inspectors.
Head chef, Craig Van Der Meer, said: "To achieve three rosettes in such a short space of time is testament to the passion and hard work the team at Stoke Place show every day.
"We will continue to improve and push the limits to ensure we continue to progress in what is a very challenging and evolving industry."
The award follows on from last year's successes of winning two rosettes and being awarded a rating of four by the Good Food Guide.
Mr Van Der Meer added: "It has taken a lot of hard work to achieve three AA Rosettes and this is another milestone on our journey to achieve the highest recognition for our food."
The talented chef, who serves up an artful twist on a traditional country house menu, is aiming to make the restaurant 50% self-sustainable by 2013.
They are currently operating at 25%, with meat and dairy sourced from farms within 50 miles and bread, jams and chutneys made on the premises.