I applied online. The process took 2 days. I interviewed at Chipotle (London, England) in May 2015
Interview
Initial interview for a new opening at Liverpool Street was standard fill out a form affair and tell us about yourself. I was invited to a trial shift a few hours later at the Islington chain. Arrived on time and they were not even expecting me, but gave me the shift anyway. Taught a bit of food prep and serving skills. They require you to speak to all staff members during the shift, and take a final interview with the store manager.
Ultimately didn't get an offer as I suspect they are looking for more long-term employees. The employees are all friendly and supportive however.