Meghan's As Ever product costs 112 pounds ($A215) and features an illustration of her Californian home, just over a month after the duchess moved back to the United Kingdom.
The inside of the box includes the words "A magical celebration of the season" and adds that the 24 handcrafted chocolates are there to "sweeten each day" and have been "thoughtfully inspired by our Montecito garden".
Meghan and Prince Harry relocated to the UK at the end of August, six years after quitting the working monarchy for a new life in the United States.
The limited edition product, which has been created in collaboration with Los Angeles chocolatier Compartes, was added to As Ever's website for pre-order on Thursday.
The festive ware is not available to buy for delivery to the UK, with Meghan's brand which includes flower sprinkles, jam and wine currently only shipping inside the US.
The site said the calendar's "flavours draw from California's fresh bounty" and feature As Ever's signature strawberry, raspberry, blackberry and orange marmalade spreads, a special chocolate finished with Meghan's flower sprinkles and a Compartes rich dark chocolate ganache truffle.
It says: "Each piece is finished with its countdown number in Meghan's personal penmanship, hand-painted in edible gold luster".
The description adds: "This limited-edition advent calendar reveals 24 handcrafted chocolates in a keepsake design inspired by Meghan's Montecito home and garden."
The duchess was pictured on As Ever's Instagram smiling as she opened one of the calendar's numbered doors while sitting on a window seat in a neutrally-decorated room.
Meghan earlier posted footage on her social media account of herself driving a golf buggy, with Compartes' chief executive Jonathan Grahm sitting at her side.
The story was captioned "Christmas planning in June" and Meghan smiled and said "Hang on" as they drove along a path, with Grahm saying "Stay tuned".
The footage also showed colour sketches of the house, and the Sussexes' labrador Pula carrying a soft toy in the shape of an As Ever pot of strawberry jam.
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