Prepare the Beef: In a large pan, place 2 pounds of lean ground beef and cover it with 1 quart of cold water. Bring to a boil over medium heat, breaking up the beef into fine pieces with a fork. Cook until the meat is thoroughly browned and cooked, about 30 minutes.
Drain Excess Fat: After the meat is cooked, drain off any excess fat from the pan to avoid a greasy final dish.
Add Aromatics: Stir in 2 finely chopped onions, 4 minced garlic cloves, and 2 tablespoons of vinegar. Cook for 5 minutes until the onions begin to soften.
Incorporate Tomato Sauce: Add 1 (15-ounce) can of tomato sauce to the meat mixture, stirring to combine.
Mix in Seasonings: Add ¼ cup of chili powder, 1½ teaspoons of salt, 1 teaspoon of ground cumin, 1 teaspoon of ground cinnamon, and ½ teaspoon of ground cayenne pepper. Stir until the spices are well mixed.
Add Unique Ingredients: Incorporate ½ (1-ounce) square of unsweetened chocolate (or substitute with 1 tablespoon of cocoa powder), 2 teaspoons of Worcestershire sauce, 5 whole cloves, 5 whole allspice berries, and 1 bay leaf into the mixture.
Simmer the Chili: Bring the mixture to a boil, then reduce the heat to a simmer. Let it cook uncovered for about 3 hours, stirring occasionally. If the chili gets too thick or starts to stick to the bottom of the pan, add more water as needed.
Adjust Seasonings: Taste the chili and adjust the seasoning if necessary. You may want to add extra salt, cayenne pepper, or chili powder according to your preference.
Cool and Store: For a healthier version, cool the chili and refrigerate it overnight. The next day, skim off any solidified fat from the top before reheating.
Serve: Serve the Cincinnati chili over cooked spaghetti and top with shredded Cheddar cheese, diced onions, and red kidney beans if desired.