In a medium saucepan, cook beef and onion until beef is brown. Drain fat. Stir in beans, tomato saue, beef broth, chili powder, chocolate, vinegar, pumpkin pie spice, and salt. Bring to boiling. Reduce heat. Cover; simmer about 15 minutes.
Meanwhile, cook pasta according to package directions.
To serve, divide pasta among 4 plates. Make a well in the center of each. Top with meat sauce and sliced onion, if desired; then cheese. Makes 4 servings.