Shares of Shake Shack (SHAK Quick QuoteSHAK - Free Report) gained nearly 3% on Wednesday as the stock continues an impressive streak that has stretched over the past month. After a rough start to the year, Shake Shack has rebounded and shares are up over 12% in the last four weeks.

It’s hard to tell exactly what about Shake Shack has impressed investors recently, but the most likely answer is the company’s well-defined expansion policy. After announcing the opening of the burger chain’s fourth Chicago location last month, Shake Shack CEO Randy Garutti sat down with the Chicago Tribune in an effort to explain that policy.

Garutti made it clear that Shake Shack was not going to get caught up in the increasingly competitive landscape of the fast-casual burger market and instead it would focus on growing at a pace that’s most appropriate for the company. The chief executive also explained that Shake Shack was working outside of its typical storefront locations.

“Surprisingly, even to us, Shake Shack is working in all kinds of different formats. We've done everything from train stations to baseball stadiums to urban core to suburban. I think you'll see us targeting more of the urban core of Chicago. There's just so much opportunity,” said Garutti.

Garutti also explained that Shake Shack recently opened its first mall-front location at the Mall of America. While Shake Shack has seen success in nearly every type of location it has opened, Garutti also made it clear that the company will not over-expand.

“We've said that we think there can be about 450 Shake Shacks in the country. But other than that we don't really set a goal. We don't talk about a specific number other than if people keep lining up to eat our burgers, we're going to keep opening restaurants,” he said.

Besides pushing the envelope with new types of restaurant locations, Shake Shack has also decided to mix up its menu. The company debuted its “Chick’n Shack” chicken sandwich in January, and now it looks like the company is ready to test out more breakfast options.

In fact, Shake Shack’s breakfast menu, which includes three sandwiches, coffee, and orange juice, is currently available in four airports around the world and will soon become available in its first non-airport location.

Shake Shack breakfast will be available during the morning hours at the company’s new Fulton Center location. The Fulton Center is a major transportation hub that connects several of New York City’s busiest train lines.

It’s unclear whether Shake Shack has any plans to expand breakfast outside of its transportation-based locations, but it is certainly something to keep an eye on.

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