Recipe invented by my girlfriend.
Brown a one-pound roast in olive oil on the stovetop in a Dutch oven or large stock pot or something. I recommend owning a large stockpot and dirtying up only one piece of large cookware.
After it has browned, filet it, then add enough water to cover it while it is not actually in the pan. Chop up about 5 garlic cloves. You can either put them in straight, or put them in a tea infuser if you don't like the texture of cooked garlic bits (this is what I did). Make certain the tea infuse is immersed. Pour or squirt in some lime juice, perhaps a teaspoon or two. Add 2 tsp adobo, 2 tsp cumin, 1 tsp cilantro, 1/4 tsp cloves, 1 tsp oregano, and 2 tsp ground chipotle chili powder. Place fileted roast (I used a rump roast, but cow cheeks are the most popular for beef barbacoa) in the mixture, bring to a boil, and reduce to a simmer for ever. I mean, I lost count of how many hours, but I did turn it off several times, brought it back to a boil, and began simmering some more. Continue this, oh, maybe 6 hours, maybe 10, I've really no clue, until the meat starts to fall apart when you try to pick it up with a fork. Remove the meat, it will sort of fall apart on you, and shread it/reduce it to itty bitty bits. Put it all back in the pot and boil it for a while so that the juices and spices work their way all the way through. Add more adobo powder and chipotle chili, to taste. Grind some [B]fresh ground pepper[/n] into the mixture. If you feel it needs anything else, if some flavor seems lacking, put some in to taste. It's fully cooked meat, so you can taste the broth to see if it's right.
It doesn't taste exactly like what you get at Chipotle's, but it's its own unique dish and I'm glad I have invented my own.