Thomasina did the Ballymaloe Cookery School 12 Week Certificate Course in January 2002, and has gone on to great success.
After Ballymaloe, Thomasina spent a short time making Gubbeen Cheese in Schull, West Cork, and travelled around Ireland with Clodagh McKenna selling homemade pasta, sauces and sourdough breads that they would make all night to sell all day.
Moving back to London, she managed a shop, Villandry and spent two years creating and editing a book called Soup Kitchen, which raised money for homeless charities with Annabel Buckingham. In 2005 she won the BBC TV cookery competition MasterChef. After that, she did a stint at Petersham Nurseries under Skye Gyngell. She has made two series of cookery programmes for Channel 4 with co-presenter Guy Grieve, Wild Gourmets in 2007 and A Cook's Tour of Spain in 2008. In 2011, she presented Mexican Food Made Simple for Channel 5.
She is Co-Editor with Annabel Buckingham of the cookbook Soup Kitchen. She has also written Cook: Smart Seasonal Recipes for Hungry People, The Wild Gourmets: Adventures in Food and Freedom, with Guy Grieve, and Mexican Food Made Simple.
Thomasina opened the first of her own restaurants, Wahaca, in the West End of London in August 2007, focusing on Mexican Market foods, using well sourced British meat, sustainable fish (she works very closely with the Marine Stewardship Council) and also, they recycle everything down to food waste. In October 2008 a second Wahaca opened at Westfield in London.
Since then she has opened two further restaurants in Canary Wharf and Soho and in 2011, Wahaca launched their first mobile street kitchen, selling Mexican street food on the streets of London. Thomasina supports NABMA, the National Association for British Market Authorities too; they are trying to get the government to lend more planning and logistical support to them which in turn will help unemployment, sustainability, a better community spirit, get people more into food and cooking and cut down on packaging.