The mother and daughter have not been seen together in public since the royal wedding on 19 May.
Harry looked extremely proud as he and Meghan's mother Doria listened to her addressing the women from the Hubb Community Kitchen at the launch event.
Meghan quickly got stuck in, preparing food that was laid out on trestle tables, dishing out green rice and later flipping chapatis and then watching kofta kebabs, turning them so they browned evenly.
The Duchess, who hosted a lunch for the women of the Hubb Community Kitchen and their families, said she had felt "immediately embraced" by the women of the kitchen who made her feel welcome on a personal level.
The duchess wrote the foreword for Together, which is in bookshops from Thursday but has been available to order online for a few days.
She said the project had been a "tremendous labour of love".
For the kickoff of the culinary guide, for which Meghan wrote the heartfelt foreword, she stepped out in a characteristically stylish ensemble including a skirt by friend and favorite Misha Nonoo, and a turtleneck bodysuit by Tuxe.
It remains to be seen, however, whether the American duchess was forced to spell "endeavour" with the British "ou", or whether she did it out of her own volition.
The 37-year-old said she was "so proud" to live in a city with London's diversity as she delivered her speech without any notes. "There's 12 countries represented in this one group of women".
Hear more on Meghan's latest project in the video below.
She continued: "Everyone embraced this so deeply because it's been a passion project for all of us, and for very good reason".
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.
You can preview two of the recipes featured in the book here on HuffPost UK.
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