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.
Remove the bay leaf. Reheat gently over medium heat. Serve over hot, drained spaghetti. Top with shredded cheddar cheese.
Fat Control and Meat Texture
Replacing standard vegetable oil with rendered beef fat alters the viscosity of the initial onion sweat, though vegetable oil at one tablespoon is standard here to soften the alliums without introducing competing flavors. Browning two pounds of ground beef requires breaking the protein clumps apart with a wooden spoon immediately upon contact with the pan to maximize surface area contact with the hot metal, which generates desirable Maillard reactions before any liquid is introduced. When adding the liquids, incorporating two cans of beef broth alongside the tomato sauce creates a thin, highly fluid base rather than a thick paste; this watery consistency is chemically necessary because the chili must simmer uncovered or partially covered for ninety minutes to concentrate flavors without burning the suspended spices.
The Chemistry of Sweet Spices
Combining ground cinnamon, cloves, allspice, and unsweetened chocolate alongside a massive quarter-cup of chili powder relies on fat-soluble flavor extraction, meaning the aromatic compounds in these spices require the fat content from the beef and oil to fully disperse across the palate. Cayenne pepper provides capsaicin, which is heat-stable and distributes evenly throughout the thin broth over the long cooking window. Allowing the mixture to reach a rolling boil before dropping the heat to a low simmer activates the starches and pectin in the tomato sauce, thickening the sauce slightly despite the high liquid volume. Although two tablespoons of cider vinegar are added during the simmer, much of the sharp acetic acid volatilizes during the ninety-minute reduction, leaving behind a subtle brightness that cuts through the rich twenty grams of fat per serving.
Resting and Rethermalization
Refrigerating the finished pot overnight is not merely a convenience step for advance meal preparation; it allows the dispersed fat to solidify and separate for easier skimming if desired, while giving water-soluble flavor molecules time to thoroughly permeate the muscle fibers of the ground beef. Reheating the chilled chili gently over medium heat ensures the dairy fats in the final cheddar cheese topping melt smoothly upon contact rather than oiling off into a greasy pool when ladled over hot, drained spaghetti.