D.C. restaurateur Mark Kuller in Barcelona, Spain, in 2010. (Charlie Mahoney/ For The Washington Post)

Mark Kuller, a former tax lawyer who transformed his prodigious appetite for good food and drink into a diverse collection of critically acclaimed restaurants in Washington, died Oct. 16 at his home in Bethesda, Md. He was 61.

The cause was pancreatic cancer, said his daughter, Candace Kuller.

The son of a bookie who took bets for the Mafia, Mr. Kuller went on to become, according to the New York Times, “a major player in corporate tax shelters.” As part of his job studying tax codes and entertaining clients, he developed a serious interest in restaurants that eventually spurred his desire to change careers.

In less than a decade and with no previous experience in the hospitality business, Mr. Kuller launched three restaurants, involving himself in every detail of the construction and concept creation.

He collaborated with Haidar Karoum, a respected chef who used to work at Asia Nora in Washington, to research and develop restaurants specializing in modern American cooking (Proof), Spanish cuisine (Estadio) and the food of Southeast Asia (Doi Moi). In 2013, Mr. Kuller opened a craft cocktail bar, 2 Birds, 1 Stone, in the basement of Doi Moi with mixologist Adam Bernbach.

All four would make appearances on best restaurant and bar lists, including those from The Washington Post and Washingtonian critics. “When visiting foodies ring me up, I’ll frequently introduce them to Proof,” Post food critic Tom Sietsema wrote in his 2009 dining guide.

Those closest to Mr. Kuller called him “Grande,” a reference not just to his 6-foot-6-inch frame, but also to his booming, bear hug of a personality. He was a man who, colleagues say, wasn’t always right, but who rarely doubted himself.

“He’s a force of nature,” said Karoum. “The way he lives really built my confidence — not that I wasn’t confident, but having someone who’s such an incredible personality and an incredible human being being behind you . . . it’s had a huge impact on my life.”

The ease with which Mr. Kuller seemed to shift into the culinary world belied the massive amount of research he conducted before launching Proof, his first restaurant. It opened in 2007 in the Penn Quarter neighborhood, across from the National Portrait Gallery.

Mr. Kuller filled folders and binders with countless research materials, covering all aspects of restaurant construction and operations, from decor to automatic wine delivery systems.

“He’s a very smart guy,” said Bill McKee, a partner in the Washington office of Bingham McCutchen, who worked with Mr. Kuller several times throughout their legal careers. “He doesn’t leave anything to chance.”

If Mr. Kuller had carved a new career path for himself in his 50s, he had also created a new life at home. In 2010, he married Kristin Connor, who was more than 20 years his junior, and started talking about being a father again. (Mr. Kuller had divorced his first wife, the former Janet Goldberg, in 2003, according to a Washingtonian profile; he had two children from that marriage, Max and Candace, who both work at their father’s restaurants.)

But last year, just days after Mr. Kuller learned Connor was pregnant, he received tragic news: He was diagnosed with stage-four pancreatic cancer, a condition with a short life expectancy.

Mr. Kuller, his friends said, began to divide his days into short-term goals. The first was to apply his research skills to seek out the best cancer treatments and medicine. The second was to live long enough to, at the very least, see the birth of his twins.

On Jan. 29, he tweeted a blurry photo of two pink newborns. He wrote: “Hello world! Meet Ida Lillian Kuller and Cash Prescott Kuller. Mama Kristin doing great!”

Within weeks, the new parents’ joy turned to grief. Ida Lillian died in her crib in April. Mr. Kuller’s survivors include his wife, Kristin, and their son, Cash, both of Bethesda; his children Max Kuller and Candace Kuller, both of Washington; and a brother, Jason Kuller of Bethesda.

Mark Alden Kuller was born on Dec. 6, 1952, and grew up in Monticello, N.Y., a town in the Catskills region. His mother, Mildred, kept a kosher household and devoted her free time to charities; his father, Sol, was a bookie for the Mafia, according to food critic Todd Kliman’s profile of Mark Kuller in the September 2013 issue of Washingtonian.

Wrote Kliman: “If anyone asks what your father does,” Millie instructed the boys, “you tell them he sells clothes.”

Mr. Kuller was a 1975 finance and accounting graduate of New York University and received a law degree from the University of California at Los Angeles in 1978. He moved to Washington in 1982 when McKee hired Mr. Kuller to serve as a lawyer-adviser in the Treasury Department’s Office of Tax Legislative Counsel. Two years later, Mr. Kuller served as a special assistant to the chief counsel of the Internal Revenue Service.

He moved into private practice in 1986 when he started working with McKee again at King & Spalding, a Washington firm where Mr. Kuller would become a partner. More than a decade later, in 1999, Mr. Kuller and McKee became founding partners of McKee Nelson.

In 2004, a federal judge singled out Mr. Kuller for criticism for his role in helping Long-Term Capital Management, a giant hedge fund that collapsed in the late 1990s, take $106 million in tax deductions.

Toward the end of Mr. Kuller’s legal career, McKee said, “he sort of lost his passion for the law, which is understandable. He had set his sights on something else.”

McKee was not surprised when his colleague finally left the law field in the mid-2000s to open Proof. By that point, Mr. Kuller’s reputation as a gourmand was firmly established among McKee Nelson clients when each year he would coordinate the firm’s annual holiday dinner.

Mr. Kuller’s annual task was made easier by the fact that he seemed familiar with the chefs and maître d’s at major restaurants from coast to coast. “Mark seemed to know everybody in the business,” McKee said. “He was able to get dinner reservations for friends at places where it was impossible to get reservations.”

When he finally opened Proof, Mr. Kuller no longer had to worry about securing reservations. Nor did he have to fret about finding a good bottle of wine on the menu. He could choose from one of his own 7,000 bottles, a collection the owner had carefully amassed over the years. It included, among other rarities, a bottle of 1961 Château Latour, which will cost a diner around $7,000 to pop open.

In his official restaurant bio, Mr. Kuller liked to tease his offspring that he planned to leave no bottles for them, including Max, who serves as wine director at Estadio and Doi Moi.

“His next goal,” Mr. Kuller’s official bio reads, “is to make sure that none of the 7,000 bottles that reside in his private cellar are left for his four beautiful children, Max, Candace, Ida and Cash.”