Jason, maybe you could ask Michels what beans they use...though suspect they may not know as it will come through their franchising arrangement. The coffee cart guy may be a bit more knowlegeable or at least find out for you.
There are quite a few coffees that have that chocolatey flavour though this is accentuated or diluted in some cases with other variable like grind, milk type and equipment used.
Maybe if you ask the above to purchase a few beans to take home, you could try them at home to eliminate some of the variables Ive mentioned as a starting point to your quest?
ps. if all else fails, put some dark chocolate in your coffee!