Cheesy Vegetable Soup

5 cubed potatoes
2 cups sliced carrots
1 cup diced onions
2 cups chopped celery
2 cups chopped broccoli
6 cups chicken broth

Sauce ingredients:
1 stick butter
1 Tbsp mustard
½ cup flour
1 tsp salt
½ tsp pepper
2 cups milk
12 oz American cheese slices

Put first set of ingredients into crockpot and cook on low for 4-6 hours or until vegetables are soft. 30 minutes before serving, prepare sauce: On the stove melt butter, then add flour, mustard, and pepper. Slowly add milk and cook on medium heat until thickened. Add sauce to crockpot along with cheese. Stir until melted.