1. In a large pot, cook the ground beef over medium heat until browned. Drain excess fat.
2. Add the chopped onion and garlic to the pot. Cook until the onion is translucent.
3. Stir in the chili powder, cinnamon, cumin, allspice, cloves, salt, and pepper. Cook for another minute.
4. Add the unsweetened chocolate, beef broth, tomato sauce, apple cider vinegar, and Worcestershire sauce. Stir well.
5. Bring the mixture to a boil, then reduce the heat and let it simmer for 2 hours, stirring occasionally.
6. Serve the chili over cooked spaghetti. Top with kidney beans, shredded cheddar cheese, chopped onions, and oyster crackers if desired.