How to Make It
Heat a large skillet over medium-high. Add beef, onion, paprika, salt, cinnamon, cumin, allspice, and garlic. Cook, stirring to break beef into small pieces, until browned, about 8 minutes. Transfer mixture to a 6-quart slow cooker. Add tomato sauce, beans, broth, vinegar, and chocolate. Cover and cook on LOW until beans and onions are tender and flavors meld, about 8 hours.
Cook spaghetti in salted boiling water according to package directions; drain. Serve chili over spaghetti. Garnish with cheese and onion.