Preheat oven to 325°. In an ovenproof Dutch oven, heat oil over medium-high heat. Sprinkle beef with salt and pepper; brown in batches. Remove with tongs., Reduce heat to medium. Add carrots and onion to drippings; cook, stirring frequently, until starting to brown, 3-5 minutes. Add cocoa; toast, stirring frequently, until aromatic, 1-2 minutes. Add tomato sauce and beer, stirring to loosen browned bits from pan. Bring to a boil; simmer 2-3 minutes. , Return ribs to pan; add water, if necessary, to cover. Bake, covered, until meat is tender, 2-1/2 to 3 hours. Remove from oven; drain, reserving juices. When cool enough to handle, remove ribs from pan and remove meat from bones; discard bones. Shred meat with 2 forks. Skim fat from reserved juices. Return meat and juices to Dutch oven; heat through. Serve on tortillas with pico de gallo and queso fresco.