Q&A With Shake Shack's Mark Rosati

Sure, In-N-Out has a head-start on Shake Shack, Danny Meyer's growing, high-quality fast-food burger chain, but the Shack has been replicating: Citi Field, the Upper West and Upper East Sides, the Theater District, Miami, and soon, Washington DC and Dubai. But burgers aren't the only things beloved by Shack fans. The frozen custard has people lining up too. Mark Rosati, Shake Shack's sunny culinary manager, recently agreed to talk about custard where it all began, Madison Square Park.

How did you get into ice cream making?

I went to school to be in film, but I was a huge fan of Gramercy Tavern. I happened to meet Tom Colicchio and John Schaefer, and I told them how much I loved it. They were like, "You're either insane or you're just really into what we do." They invited me to work in the kitchen and gave me about three buckets of onions to slice. The whole time I was just like, "I can't believe I'm in this kitchen!" Six hours later I was still smiling and they were like, "Okay then, you're serious about this." I worked for three years as a cook, and I'd also hang out in the pastry kitchen where I learned a lot from people like Claudia Fleming and Nancy Olson. I came here as a manager.

How many flavors do you do a year?

About 70 to 80 flavors. We repeat some.

How many are there total?

There's a database of about 300 flavors. They break down into three categories. Ones we don't love, ones we still like to tweak, and then the outstanding ones, the ones that really, really pop. There are at least a hundred of those.

What are the Top 5 most popular flavors?

Salted Caramel, Coffee & Donuts, Mint Chocolate Chip (which is made with Valrhona), Sweet Corn, and Cinnamon Toast. Salted Caramel is the most popular, but Coffee & Donuts is really coming up strong.

Anybody whose ice cream you've been particularly inspired by?

Meredith Kurtzman's Olive Oil Gelato. It's an amazing, amazing gelato. Maybe the best in New York.

How do you come up with inspiration for flavors?

It's about harnessing your inner child and taking you back to the experience of enjoying things for the first time.

How do you decide which flavors go on the calendar?

We like to have a couple of foodie flavors. I like to have something from the greenmarket, and some classic flavors. Each month we try to mix it up. We do three to four seasonal flavors. Salted Caramel we do three to four times a years. People are always e-mailing us to ask, "When's it coming back?"

What's your favorite?

Coffee & Donuts, and Thin Mint, our take on the classic girl scout cookie.

How is it that the Shack's custard is so soft?

The custard recipe has a lot to do with it, but a lot of it is the machine, and the fact that it's made fresh and doesn't sit in the Shack for more than an hour or two so there are no ice crystals. It has a thickness and creaminess that you don't always get with soft-serve. It really lends itself to milkshakes.

Can you tell us anything about the ingredients that go into the custard?

I can tell you that the milk is full on. We've tasted alternatives and you just can't get the same product without whole milk.

Are there ingredients that you use in the custards that come from local businesses?

Buttercup Cake Shop makes the red velvet cake we use in our Red Velvet Custard. There are Doughnut Plant doughnuts in our Coffee & Donuts. That was a no-brainer. We used bacon peanut brittle from The Redhead, and chocolate from the Mast Brothers.

Do you ever create flavors based on peoples' email suggestions?

Some are made that way, and there are some that the staff has suggested, but mostly it's about us conceptualizing.

Any challenges involved with bringing the custard program to Dubai?

Yeah, there are some. We're going to have the same calendar but we'll remove two flavors every month and add two flavors that are relevant to the region. So for instance, the orange creamsicle will change to include rosewater. You'll see other things like dates, figs, and some of the unique honeys and spices that you can find in the region. I'll be going there next month. I'm really excited about the spices. It's of a quality you're really not used to.

What are the strangest flavors you guys have done?

The most bizarre was Heirloom Tomato. That was a difficult one to nail. What we learned was that it had to be made using really, really good heirloom tomatoes, with a little bit of basil and a little bit of almond. Raspberry Jalapeño. I liked it but some people said it was too spicy. Mint-cucumber was refreshing but we needed to use too many cucumbers to make it and there was too much water.

What's with the all specialty items at other Shack locations, but no specials at the original location? Is it because the kitchen is smaller here?

Well, the kitchen is smaller here, but we did run a standing order at Madison Square Park. It's really just that it's so busy here. But I can tell you that we're playing with some things for the cold weather. We may have some warm items coming your way.

Is there a question that you wish you were asked more about the custard program at Shake Shack?

Well, my favorite question is, "Is there gluten in the custard?" The answer is, there is not. But I guess the most important question is, "What is custard?" It's simply fresh ice cream that's rich and creamy in texture because there's a little more egg and a little less air.

Any specials we can look forward to?

The Shackenstein, chocolate custard with candy corns. It's going to be a deconstructed Hostess Cup Cake. It's going to be dyed green and there will be frosting and cake in it and the custard base will have marshmallow in it. That will be available at all locations.