"Our Community Cookbook" showcases more than 50 recipes from women affected by the Grenfell Tower fire.
"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.
Shortly after the fire broke out in 2017, a group of women set up the community kitchen, to prepare fresh food for those affected.
A portion of the sales will go to help the Hubb Community Kitchen "to strengthen lives and communities through cooking", the press release reports.
The duchess visited in January and has continued to make regular private visits.
During her visits, the Duchess learned that the kitchen was only open on Tuesdays and Thursdays, and when she asked why it wasn't open seven days a week, the group revealed it was down to lack of funding.
In her introduction for Together: Our Community Cookbook, she writes: "I immediately felt connected to this community kitchen; it is a place for women to laugh, grieve, cry and cook together".
Meghan joined the women for a meal at the Al Manaar Muslim Cultural Heritage Centre in West London
Proceeds from the book, which will be released on Thursday in the United Kingdom, will support the Hubb Community Kitchen, helping it to stay open and to thrive, so it can widen its reach to others in the community and beyond.
Penguin Random House chair Baroness Rebuck said the company was instantly caught up by the extraordinary vision for this project.
Kensington Royal shared videos and a photo of the women of the Hubb Community Kitchen cooking with the royal.
Husband Prince Harry will be at the party, too, but this latest engagement on the royal couple's diary is mostly focused on Meghan's burgeoning charity work as the newly minted HRH Duchess of Sussex.
"But most of all "Together" is an homage to life and friendship and we hope it will act as a symbol to all communities and encourage cooking together for life and joy". "Especially after the disaster of Grenfell, when people had to feed their children every day and had no space to cook, this kitchen created the love, created the atmosphere for people to come together over food, and since then we've carried on doing that together".