The upstart coffee chain has a larger expansion opportunity right now.Chipotle Mexican Grill (CMG 2.92%) has long been an investor favorite, and for good reason. It has delivered fabulous gains for shareholders who've stayed with it through thick and thin. Its opportunity is far from over, but it already has 3,500 restaurants, and growth investors might be on the lookout for some fresher picks.It's not easy to successfully grow a restaurant chain, but Dutch Bros (BROS 2.17%) looks like it's on its way, and ...