Place The Chicken Breasts Into A Slow Cooker. Whisk The Cream Of Chicken Soup, Cream Of Mushroom Soup, Sherry, Garlic, Celery Flakes, And Paprika In A Mixing Bowl. Stir In The Parmesan Cheese And Mushroom Pieces; Pour Over The Chicken. Cook On Low For 8 Hours Until The Chicken Is Tender, And The Sauce Has Reduced Slightly.