In a large skillet, heat 2 tablespoons butter over medium heat. Brown chicken; transfer to a 5-qt. slow cooker. Add remaining butter to skillet; saute onion, carrots and celery until slightly softened. Add garlic; cook 1 minute longer. Transfer onion mixture to slow cooker; add next 8 ingredients. Cook, covered, on low 4 hours or until carrots are tender. , In a small bowl, mix cream and cornstarch until smooth; gradually stir into soup. Cook, covered, on high 15-20 minutes or until soup is thickened. If desired, sprinkle with parsley.