The cause was cardiac arrest, said a friend, Nicole Mabry. Ms. Powell was a bored administrative assistant living in a cramped New York apartment in her early 30s when she began her work in 2002 in “one of those panicked moments,” she later told The New York Times. Her blog, the Julie/Julia Project, was a humorous, idiosyncratic catalog of her attempt to cook all 524 recipes from her mother’s dog-eared copy of Mastering the Art of French Cooking, Child’s 1961 classic , which required her to search the grocery stores. shops and butchers for rare ingredients (kidneys, sweetbreads) and learn to peel potatoes in the shape of an olive. The blog brought her a wide audience and eventually a publishing deal. Her book, “Julie & Julia: 365 Days, 524 Recipes, 1 Tiny Apartment Kitchen” (2005), sold nearly 1 million copies and was made into a 2009 film. Written and directed by Nora Ephron, “Julie & Julia” starred Amy Adams as Mrs. Powell, whose story was intertwined with that of Child (played by Meryl Streep) and Child’s husband Paul (Stanley Tucci). A full obituary will be published soon.