Crockpot Cheese Soup

2 Stalks celery, chopped
2 Carrots, sliced
3 Green onions, chopped
1/2 Stick butter
2 (10 1/2 oz) Cans chicken broth
2 (11 oz) Cans cream of potato soup
1 (8 oz) Package pasteurized process cheese spread, cubed
1/8 Teaspoon salt
1/4 Teaspoon pepper
8 Ounces sour cream

In a skillet, brown ground beef, drain and transfer to 3 to 4 quart crockpot sprayed with vegetable spray. Add remaining ingredients plus 1/4 to 1/2 cup water and stir well. Cover and cook on LOW for 1 1/2 to 2 hours. Stir once or twice during cooking time. Add a little salt if desired. Serve hot with chips or spread on crackers.