Heat oil in a large saucepan over medium heat. Add onion and cook, stirring frequently, until tender, about 6 minutes.

Add beef, in batches if necessary, and cook, breaking up with a wooden spoon, until browned.

Add chili powder, cinnamon, cumin, allspice, cloves, bay leaf, chocolate, beef broth, tomato sauce, cider vinegar, and red pepper. Stir to mix well. Bring to a boil. Reduce heat to low; cover and simmer 1 1/2 hours, stirring occasionally.

It is the best if you now refrigerate overnight so chili thickens and flavors heighten.

In a large pot, boil spaghetti noodles to al denté, about 8 minutes.

Remove the bay leaf. Reheat gently over medium heat, add 1/4 cup shredded cheese. Serve over hot, drained spaghetti on hot plates. Top with remaining shredded cheddar cheese.