Place the rib tip trimmings, garlic, onion and bay leaf in a #12 cast iron dutch oven. Top with salt, red pepper flakes, cumin, cinnamon, chili powder, and coriander. Add 1/2 of the beer.

Cover and place over direct heat on a 350f degree grill and cook for 1 hour.

Add second half of beer, stir, cover and continue cooking for another 30-60 minutes, until the meat is fork tender.

Remove the meat to a cutting board and shred, separating the fat and bones from the meat. Add the shredded meat back to the cast iron and toss in the rendered fat. Return to grill for another 10 minutes then serve with tortillas and toppings (black olives, grilled corn, tomatoes, black beans, diced onion, cheeses, lettuce, etc)

Adapted from: http://www.examiner.com/x-396-Chicago-Dining-Examiner~y2009m3d9-Recipe-Crock-Pot-Carnitas-it-doesnt-get-easier-than-this