Whisk the raw ground beef into the cold broth in a 6-quart crockpot until no clumps larger than a pea remain.
Stir in the onion, garlic, tomato sauce, chili powder, cocoa, cumin, cinnamon, allspice, Worcestershire and salt.
Cover and cook on low for 7 to 8 hours, stirring firmly after 2 hours to break up any meat that has gathered together.
Check that the beef has reached 160°F, then skim any fat from the surface.
Stir in the vinegar and cook uncovered on high for 20 minutes until the sauce is loose but no longer watery.