Heat a large pot over a medium-high heat. Add the olive oil and onions and stir. Add the ground beef and cook until well caramelized. Deglaze the pot with 1 cup of the beef stock. Add the remaining 4 cups stock and simmer for 15 minutes.
Add the tomato sauce, chocolate, chili powder, vinegar, Worcestershire, cinnamon, cumin, salt, cayenne, allspice, cloves, garlic and bay leaf. Simmer, uncovered, for 1 hour.
To create your own Cincinnati chili experience, try serving the chili in any of these combinations:
Classic 2-Way: chili and spaghetti
Classic 3-Way: chili and cheese
Classic 4-Way: add onions or kidney beans
Classic 5-Way: add onions and kidney beans
Cheese Coney: on a hot dog with yellow mustard and cheddar (onions, optional!)