In 1997, New York’s SoHo, then decidedly more low-key and artsy, was shaken up by the arrival of the upscale, bustling brasserie, Balthazar. Soon, celebrities started flocking to the mirror-and-banquette-filled hangout for croissants and plateaux de fruits de mer. They joined early devotees like writer Reggie Nadelson, whose At Balthazar: The New York Brasserie at the Center of the World (Gallery Books, April 4), will publish to coincide with the restaurant's 20th anniversary. It's a deep, unrestricted dive into the restaurant’s persistent allure.

We chatted with Nadelson about Balthazar's consistency in a shifting SoHo.

How did the project first start brewing?

It took about ten years of nagging. I went to Balthazar for breakfast a lot and one day in 2003, right after I wrote a piece for a magazine, Keith [McNally, the restaurant’s owner] told me he wished I had written the intro to the Balthazar cookbook. Instead, I begged him to let me do this book. He was reluctant. Finally, in 2014 he said okay. I grew up in Greenwich Village and have always lived in restaurants. I love the culture.

At Balthazar is a hybrid of recipes and a glimpse into one of New York’s most well-known restaurants, and to fully tell that story you travel to places like Kansas and Bordeaux, capturing the importance of Balthazar’s relationship with different purveyors. What did you want to illuminate by collecting all these different snapshots?

Keith says that restaurants have a social function, and that’s true whether it’s a brasserie, diner, or pub. After 9/11, Balthazar opened early and it was a place where people came together. A lot of the staff has worked there for twenty years. No one ever seems to leave, and if they do, they come back. I never used a tape recorder more than when talking to the chefs, dishwashers, and waiters. They come from forty different countries like Pakistan, Senegal, and the Dominican Republic, and they all manage to get along, which is an affirmation of one’s feelings about New York. I wanted to show how Balthazar is truly a microcosm of the city.

How do you think SoHo was transformed by Balthazar’s opening?

New Yorkers always complain and say SoHo was better when it had interesting shops and galleries and wasn’t yet a mall. Balthazar gave SoHo a center, but a lot of writers and artists went there, so it felt like a real neighborhood spot where we got to be friends with the regulars and waiters. Sometimes we would stay for breakfast until three p.m. It was idyllic and it very much defined SoHo as a destination. There were tourists in those days, but only those with a little bit of daring.

Your year and a half of research and writing must have led to many eye-opening moments. What is one of your favorite discoveries?

How much extraordinary effort it takes to run a restaurant. Consistency is everything, and Balthazar turns out half a million meals a year of the same quality. A perfect steak frites always needs to be a perfect steak frites. There’s one guy in a small kitchen, and he’s been peeling potatoes for twenty years. It’s not a machine. The people at Balthazar aren’t working mechanically; they really care.