Pot Luck Potato Casserole

1/4 cup plus 3 Tbsp butter, divided
1 (10 3/4 oz) can condensed cream of chicken soup, undiluted
8 oz sour cream
1/4 cup chopped onion
1 tsp salt
2 lbs potatoes
2 cups shredded Cheddar cheese
1 1/2 to 2 cups bread stuffing mix

Place 1/4 cup butter in medium microwave-safe bowl; cover loosely with plastic wrap. Heat on HIGH about 50-60 seconds or until completely melted. Add undiluted soup, sour cream, onion and salt to the butter; mix well.
Peel potatoes; cut into 1/2-inch cubes.
Combine potato cubes and Cheddar cheese in slow cooker. Pour soup mixture into slow cooker; mix well. Sprinkle stuffing mix over potato mixture. Place remaining butter in small microwave-safe bowl; cover loosely with plastic wrap. Heat on HIGH about 40-45 seconds or until melted. Drizzle butter over bread stuffing mix in slow cooker.
Cover slow cooker and cook on HIGH 5-6 hours or on LOW 8-10 hours or until casserole is hot and bubbly and potatoes are tender. Store leftovers, covered, in refrigerator.