On a recent afternoon, Ms. Brennan sat next to the unlit fireplace in her living room. As she moved a sore leg back and forth between an ottoman and the floor, she suggested that her impulse to empower employees was a rejection of restaurant industry norms she confronted as a young woman.

“In those days, no one was paying attention to developing people,” she said. “A restaurateur has to be part of a team to make something everyone can be proud of.”

Her decision to tap Mr. Prudhomme, a Cajun, to run Commander’s kitchen in the 1970s loosened the grip that European-born chefs had on American fine dining. Alongside Ms. Brennan, and later on his own, the media-savvy Mr. Prudhomme helped set the table for a renaissance in American regional cooking that has yet to abate.

“New Orleans was really the centerpiece of the whole American food movement,” the New York restaurateur Drew Nieporent said. “And Ella put New Orleans on the map.”

Ms. Brennan entered the hospitality business as a teenager working at the Old Absinthe House, a Bourbon Street bar owned by her brother Owen, 15 years her senior. She had dropped out of a local business school after deciding, as she wrote in her book, that “I wasn’t going to type for any man.”

In 1946, Mr. Brennan bought Vieux Carré, a French Quarter restaurant that Ms. Brennan described recently, with typical candor, as “terrible.” Mr. Brennan hired her to manage the business, looking to prove that an Irish family could operate a restaurant superior to established French-Creole restaurants like Arnaud’s, Antoine’s and Galatoire’s.