Tie the allspice, cloves, cinnamon sticks, and bay leaf together in a double layer of cheesecloth and place the bag in a 4-quart slow cooker.

In a large skillet, working in two batches if necessary, cook the beef over medium-high heat until no trace of pink remains, about 10 minutes. Drain off the fat, then add the beef to the slow cooker, along with the tomatoes, 1½ cups water, the onion, garlic, ground cinnamon, cumin, cayenne, Worcestershire sauce, 1 teaspoon salt, and ½ teaspoon pepper. Cook, covered, on the low setting for 6 hours.

When ready to serve, cook the pasta in a large pot of boiling water until al dente; drain well and set aside. Place the beans in a small saucepan with enough water to cover, and bring to a simmer. Cook until heated through, then drain.

Stir the chocolate into the chili until melted, then season with salt and pepper to taste. Remove and discard the bag of whole spices.

Divide the pasta among 6 serving plates, then top with a spoonful of beans, ladle chili over the beans, and top with a big mound of cheese.