You have to try "The Red Onion"
Their signature sandwich is AMAZING! I live almost 3 hours from Burlington, so I can't enjoy this little piece of heaven on a regular basis. I've tried to dublicate it, but alas I have to wait for my next visit to Church St. Taking the ferry? Get a few different sandwiches and swap with friends on the ride across Lake Champlain. See what you like best. And don't forget to grab a few of their chocolate chip cookies as well!