Place onion in a 3 1/2- or 4-quart slow cooker. Top with potatoes and chicken thighs.
Drain juices from one can of tomatoes and discard the juice. In a bowl stir together the drained and undrained tomatoes, the jalapeno pepper, Worcestershire sauce, garlic, oregano, cinnamon, and cloves. Pour over all in cooker. Cover and cook on low-heat setting for 10 hours.
Meanwhile In a small bowl stir together the snipped parsley and chopped olives.
Sprinkle Parsley-Olive Topping over individual servings.