Heat oil in a large nonstick skillet over medium heat. Add chicken; cook 3 minutes on each side or until browned. Remove from pan. Add onion and garlic to pan; cook 2 minutes or until tender, stirring constantly. Add walnuts, and cook 1 minute or until toasted and fragrant, stirring constantly. Combine flour, cinnamon, and red pepper, and sprinkle over walnuts, stirring to coat. Add broth; stir with a whisk. Return chicken to pan, breast side up. Cover and simmer 15 minutes or until chicken is done and sauce is slightly thick. Stir in parsley, vinegar, salt, and black pepper. Serve over rice.