Diana Kennedy is 95, and she’s still upset about the garlic in your guacamole.

The British firebrand and cookbook author is the subject of a new documentary called “Nothing Fancy” from Austin director Elizabeth Carroll that had its world premiere during South by Southwest. The film won the Special Jury Recognition for Excellence in Storytelling in the full-length documentary category.

Featuring home videos, personal photos, interviews with more than half a dozen chefs, music from Austin composer Graham Reynolds and unprecedented access to Kennedy and her Michoacán homestead, the documentary captures the feistiness and passion of the “adorable narcissist” who continues to teach cooking classes and travel to talk about her work.

The film focuses on Kennedy in her home about 100 miles outside Mexico City, which has become both her personal sanctuary and a living cultural center, housing the cazuelas, comales and molcajetes that Kennedy has gathered during her years of travel. “These are my treasures,” she says pulling down some of the cooking vessels in her kitchen. “Each represents a journey into someone’s kitchen or a market.”

The documentary features many quiet, poignant moments with Kennedy, as well as the defiant, funny ones when she gives culinary students a hard time about messing up rice or expresses her dismay about how garlic-loving Americans make guacamole.

It was fascinating to learn how she became an authority in Mexican cooking, even more so than chef Rick Bayless, who is interviewed in the film.

During World War II, Kennedy worked in the Women's Timber Corps, a British civilian organization whose workers felled trees. “I’ve been planting trees ever since,” she says.

On holiday in Haiti in the 1950s, Kennedy met her soon-to-be husband, Paul, who was a foreign correspondent with The New York Times. They met and married shortly thereafter, and Kennedy joined him in Mexico City.

When Paul traveled for work, Kennedy would get on a bus to head out for her own work, interviewing Mexican cooks about how they made everyday and specialty dishes, including exacting details about where they got the ingredients and the methods used to prepare the food.

In the mid-1960s, Paul Kennedy fell ill with prostate cancer, and they moved to New York City for his treatments. He died in 1967, and Kennedy says she felt “lonely at sea and shell-shocked” in New York.

She and Paul had hosted New York Times food editor Craig Claiborne in Mexico City, and Claiborne was the first to write about Kennedy’s love of Mexican food in the U.S. She had thought about teaching classes, but she didn’t actually start teaching them until he published an article promoting the classes in the newspaper.

Within a few years, Kennedy, who never remarried, was ready to plant her roots in Mexico and poured herself into her studies. Instead of riding the bus, she started driving around the country. She slept in her truck or in a hammock strung up outside. “I felt more at home the more I went,” she says.

The film touches (too) briefly on Josefina Velázquez de León, a Mexican celebrity chef who published more than 140 cookbooks from the 1930s to the 1960s and was the country’s original culinary anthropologist. Kennedy mentions that de Leon’s work inspired her own but that she wanted to build upon it to find out “how people lived and what the landscape looked like.”

During her travels, she also collected seeds and cuttings, which now grow as well-established plants in a greenhouse at her house — peppers, herbs, vegetables and fruits that Kennedy sees as integral to making the dishes as true to their origins as possible.

Naming the recipes, giving them context and giving credit to where they came from is how Kennedy earned the respect of Mexicans and culinary historians abroad. Kennedy has been recognized many times by the Mexican government for her contributions to the study of Mexican cuisine, and most of her books have been released in Spanish.

The University of Texas Press has published and reissued several of her books, including 2010’s “Oaxaca al Gusto: An Infinite Gastronomy,” “My Mexico” and “Nothing Fancy,” the 1984 book from which the documentary gets its name.

Carroll featured thoughts about Kennedy from Latin chefs Pati Jinich, Jose Andrew and Gabriela Cámara, but the film only features one interview in Spanish. Chef Abigail Mendoza, who has known Kennedy for 35 years through her restaurant, Tlamanalli, in Oaxaca, called her “an adoptive daughter of Mexico.”

What separates Kennedy from many non-Mexican chefs who have studied the cuisine is that she keeps the recipes as she learned them, not adding her own variation, and for that “the people of Mexico will be indebted to her work,” Jinich says.

Although in remarkable health and still driving, Kennedy talks about her anxieties about growing old. “I wish I could make a pact with the devil and retrace all my steps in this country. There’s too much to do,” she says, looking around her office that holds more than 60 years of papers and notes.

What will happen to her life’s work? Carroll said that Kennedy is still trying to figure that out.

Although she doesn’t use social media, Kennedy uses a computer and doesn’t shy away from sending comments to publications that get her story (or her recipes) wrong. “The more we are connected electronically, the less we are unified,” she says. “What’s life about if you can’t make yourself heard? ... Who else is going to start screaming when I’m gone?”

At the premiere at the Alamo Ritz on March 9, Carroll said she hadn’t heard about Diana Kennedy until about six years ago, when she was doing some research about Mexican culinary experts. When she searched for more information about her online, she discovered that Kennedy had a book signing in Austin the next day.

She stopped by the book talk and introduced herself to Kennedy, who was surprisingly open about having a documentary crew follow her, and over several years, Carroll and her crew went to Mexico several times for interviews, each time getting to know Kennedy a little more. At this point, she feels comfortable around the notoriously prickly author. “She hasn’t seen the film, so we’ll see how that goes.”

Kennedy’s legacy has been well-established for decades, but only now have we seen how and why she earned that respect in the first place. Carroll pored through countless hours of home videos and television clips to show the author at various stages during her life, and the footage she gathered over the past five years offers a priceless glimpse into her perseverance and quirky personality.

In one of those scenes, Kennedy’s thoughtfulness, not her prickliness, comes through. She’s cooking beans during a segment of “The Art of Mexican Cooking,” a 1992 cooking show that never aired, and she explains that sometimes things take longer than you think to accomplish. “Cooking is great therapy,” she says. “I think we need things that take a long time.”