'The important discoveries in my life have always happened by chance,' she says and Mexico was no different. She would never have ended up here at all had she not decided to make an impromptu stopover in revolutionary Haiti in 1957. There she met husband-to-be, Paul Kennedy. They married in Mexico City, where Paul was correspondent for the New York Times,
Diana was immediately struck by how extraordinary everything tasted. As she accompanied her husband on assignments, she became fascinated by the distinct foods of each region. Every village had its own recipes, dishes that had been passed down for centuries but never written down.
Upon her return to Mexico City, she'd ask her Mexican friends how to cook these electrifying dishes. "They'd laugh and send me to talk to their maids. The maids would say, 'You have to visit my village', and that's how I started driving all over the country tracking down recipes.'
She hunted down foods with the zeal of an anthropologist. Perhaps more than any culinary writer, she has served as the conduit for preserving a wonderfully traditional regional cuisine by traveling more than a million kilometers around her adopted country, alone, in a simple pickup truck, seeking sources for documenting the techniques and ingredients passed down orally in remote villages for centuries.
When famed New York Times food writer Craig Claiborne visited she gave him her favourite book of recipes. 'He refused it, saying, "I'll only read a Mexican cookbook once you have written one".'
The opportunity to do that came sooner than she would have liked. In 1967, a year after the couple had moved back to New York, Paul died of cancer. 'I was sad and worn from the experience but also needed to earn a living. Craig got me a job teaching Mexican cooking, which, at the time was almost completely unknown. One of my first students was the woman who was to become my editor. She asked me to turn the class into a book.'
That book, The Cuisines of Mexico, became a best-seller and taught a generation of Americans that Mexican food meant more than tacos, nachos and chilli con carne. What makes her books special are Diana's 'word pictures': her adventures, such as her hunt to find escamoles - 'delicious' ant eggs; a barbecue that lasts all weekend in Oaxaca; her apprenticeship in a Mexico City bakery to learn the secrets of the all-male trade. She peppers her recipes with citations from the ancient Aztec codices, as well as prayers from the Spanish nuns and priests who grafted Mediterranean cooking onto an already elaborate pre-Columbian cuisine.
With eight books under her belt and two more in the works, she has become the pre-eminent authority on Mexican gastronomy. In America she is an icon for foodie set and in Mexico she is revered - she has been awarded the Order of the Eagle, the highest honor that can be bestowed on a non Mexican. Now in her 80s, she has lived in Michoacán for many years in an extraordinary solar-powered adobe eco-house situated on a seven-acre organic ranch..
Her newest book, anxiously anticipated by her legions of fans, focuses on Oaxaca, describing both the food and the culture unique to each of the state's diverse regions.
To her, Oaxaca is a microcosm of all that is best in Mexico's cooking traditions: its intensity and imagination, ritual and art, its love of nature and privileged place within the life of a community. Her new book exemplifies her belief that cuisine is as essential a part of a nation's culture as its art or music.
"Too many chefs tend to look down their noses at Mexican food, thinking only of greasy tacos,' she says. 'But just ask them what they would do without tomatoes, chocolate, corn, turkey, squash, avocados, chillies and beans - all gifts from Mexico"
Some people set out to save Mexico's monuments from the predations of the modern age. Diana's lifelong quest has been to preserve the more intangible traditions of eating that have nourished its vibrant civilization.