The "Together: Our Community Cookbook", a collection of 50 recipes from the diverse users of the communal kitchen at the Al Manaar Muslim Cultural Heritage Centre, will be used to allow the project to expand and open for up to seven days a week.
And her message resonated more than it could have coming from any other member of the Royal family.
It's Doria's first public engagement since attending her daughter's wedding on May 19.
Without the help of any notes, Meghan thanked the women of Hubb Community Kitchen for their help in creating the 37-year-old's charity cookbook titled Together: Our Community Cookbook.
Doria Ragland, who lives in Meghan's native California, made a surprise appearance as she joined the duchess and Prince Harry at the garden function on Thursday.
"I used to call you Meghan (and I still do) but dear Duchess of Sussex your first project "Together" [is] a cookbook bringing women of all cultures together", Williams wrote.
Meghan's husband and mother looked on proudly as she gave a speech to launch the book, telling them the multi-cultural kitchen has been integral in helping her feel welcome in London after moving from Canada where she lived while filming the popular TV series Suits.
Zahira Ghaswala, the Hubb's co-ordinator who hosted Meghan's first visit to the kitchen, said: "As far as I know, on Amazon we're number one - everything's just been a positive vibe out there. I'm just as excited as you are". Everyone has embraced this so fully because it has been a passion project for us all'. Ragland gave each woman a hug and said, "It's awesome".
Meghan added. "I said in the foreword that this is more than a cookbook, and what I mean by that is the power of food is more than just the meal itself; it is the story behind it, and when you get to know the story of the recipe, you get to know the person behind it". "To be able to celebrate what connects us rather than what divides us, I believe, is the ethos of Together".