Sprinkle chicken with curry powder, garlic and salt. In a large nonstick skillet, heat oil over medium heat. Add chicken and cook until golden brown, 3-4 minutes on each side. Place sweet potatoes and onion in a 5- or 6-qt. slow cooker; top with chicken. Drain pineapple, reserving juice. Add drained pineapple, preserves and soy sauce to slow cooker. Cook, covered, on low 5-6 hours, until chicken and potatoes are tender., In a small bowl, mix cornstarch and reserved pineapple juice until smooth; gradually stir into slow cooker. Cook, covered, on high , 20-25 minutes, until sauce is thickened. If desired, sprinkle with parsley.