"But there's definitely -- there's always times, particularly when you're doing a boring, repetitious job, you start to wonder, 'Am I really getting something out of this? Did I really go halfway around the world to learn how to peel a potato?' But those are the sacrifices that you have to make, and if you're lucky, and if you're good about it, it will serve you in the end --you'll definitely learn a lot and it becomes part of the foundation of being a chef."
No matter where in the world he found himself, Mullen said, New York City was always in the background.
"New York is definitely, within the restaurant world, it's definitely a competitive environment, but I think that's a good thing," he said. "It really pushes each of us to push ourselves. To get better at what we do and to really take every day as an opportunity to learn more and to further yourself personally and professionally as a cook. I think it would be very easy if ... I weren't surrounded by so many talented people, to become complacent and to say, 'Oh, this is fine. Restaurant is doing well, we're doing okay, let's just kind of move things onto cruise control.' But you can't do that in New York. You always have to be pushing yourself."
Being a New York chef doesn't mean abandoning the small-farm, locally produced approach to food, Mullen said.
"We try not to use -- even here in New York, we try to use our seafood that comes from Long Island, or if it comes from Rhode Island, or if it's coming from Cape Cod," the chef said. "We try to buy things as locally as possible and getting our meat from the Hudson Valley and getting produce from New Jersey and Long Island - trying to keep things as close and as seasonal as possible. And that started from me from my upbringing ... as I grew up and I learned more about the importance and the impact of eating locally, it's reinforced all of those things that were kind of ingrained in me through my upbringing."
Although he's established a name as a master of Spanish cuisine, Mullen readily jumps to the defense of Irish cooking -- and not just because of the holiday. Even when he was cooking in Spain, Mullen said, Irish imports played a big role in keeping diners happy.
"I think that Irish food has gotten kind of a bad rap, but there's really a wealth of produce in Ireland and a wealth of products that are remarkable, and there's been a change, you know, in recent years, particularly in the past 10-15 years in the perception of Irish food," Mullen said. "When I was working in Spain, we actually got a lot of product from Ireland. We would get langoustines, Dublin Bay prawns from Ireland, we'd get wild salmon from Ireland. We'd get oysters ... and obviously potatoes, which grow very well in the climate. But there's really some remarkable product.
"I kind of grew up not having a real connection to my Irish heritage. Though a lot of the food that we ate was either -- because my grandmother's English -- either traditional English food or, without even realizing it, a lot of traditional Irish food that we were eating. ... Things that kind of were worked into my repertoire as a kid. The food that I grew up eating, I didn't realize was actually colcannon or it was soda bread or things that were very traditionally Irish."
Mullen said the most important thing about food is not where it comes from but whether it makes people happy.