She owns Darjeeling Express restaurant in London's Soho and was profiled on the sixth season of the documentary series Chef's Table.

In 2019 Business Insider named Khan number 1 on their list of "100 Coolest People in Food and Drink".

[11] After her aunt died, Khan returned to India for a visit of a few months[10] to continue lessons with her mother and the family's cook.

[3] In 2012,[13] after obtaining her PhD, Khan started offering a series of private supper clubs in her home for a dozen people for £35 each.

[13][11][16] She struggled early on to lead her team of home cooks, mostly local immigrants working for the first time in a professional kitchen, but then a review by Fay Maschler helped bring in customers.

[13][14][15] Simon Quayle, a regular customer and executive director of Shaftesbury, offered her the opportunity to compete for a lease in Soho.

[10] When an investor backed out, Khan's husband gave her the money she needed, although he disapproved of the business.

[3] Khan opened Darjeeling Express, a 56-seat location[7] offering Indian Rajput and Bengali[13] home cooking specialties,[4] in 2017 in Soho.

[11][14] Khan recalls Mandviwalla, who was born in Mumbai and lives in New Zealand, "did not ask me pointless questions about my husband and marriage, I did not need to explain what my mother meant to me, she got it.

[30][31] On Sundays, when Darjeeling Express is closed, Khan offers free use of the premises to women who are aspiring chefs and restaurateurs who would like to host supper clubs.

[4][14] In July 2019, to mark her 50th birthday, Khan traveled to Northern Iraq to open an all-women cafe for survivors of ISIS at the Essyan refugee camp.

[1][7][33] In 2022, she was appointed the Chef Advocate for the United Kingdom (a WFP Goodwill Ambassador) by the UN World Food Programme[34] and an Honorary Fellow of the Queen's College, Oxford.