Robbins posted a picture of the jam artfully placed inside a bowl of lemons to Instagram.
The glass jar featured an American Riviera Orchard logo with Montecito written underneath it.
According to the label, the spread is No 17 of 50 jars produced by the brand.
Robbins wrote: “Breakfast, lunch and dinner just got a little sweeter.”
In another post, she said: “I absolutely love this jam so I’m not sure I’m sharing it with anyone. Thank you M.”
Balquier, who is a friend of the couple and married to Prince Harry’s friend Nacho Figueras, posted a similar image with the caption: “Strawberry jam makes me happy. And I love your jam.”
Her pot, which was labelled as No 10 of 50, was pictured alongside a piece of bread and some fresh strawberries.
The Duchess launched her new business on March 14 after posting about the venture on Instagram.
It is thought that she intends to manufacture a range of domestic items from tableware and cutlery to cookbooks, place name card holders and placemats.
The brand will also make a range of preserves, from jams and marmalades to various vegetable-based spreads, nut butters and fruit butters.
The launch follows claims the Duchess is planning to “take on America’s most famous lifestyle queens” such as Ina Garten, Martha Stewart and Joanna Gaines, and even plans to launch a “lifestyle/food show” on Netflix.
The Duchess has been working on the initiative for more than a year.
