Mama's Cheesy-Potato Soup

This is one of my favorite meals ever - it's great with a nice green salad and a loaf of bread. This is SUCH a great "cold winter night" meal.

Ingredients:
* 4 cups peeled/cubed potatoes
* 1-1/2 cups chopped onion
* 1-1/2 cups chopped celery and leaves
* 1 Tablespoon salt
* 4 cups water
* 1 stick butter
* 1/2 cup all purpose flour
* 2 teaspoons salt
* 1/4 teaspoon pepper
* 2 teaspoons dry mustard
* 4 cups milk
* 3-1/2 cups shredded sharp cheddar cheese (I think it's best to get it in a block and shred it yourself)
* 2 Tablespoons parsley flakes
* 28 oz. can stewed tomatoes and their liquid

Directions:
* In a large kettle, combine potatoes, onion, celery, ONE teaspoon of salt, and water. Bring to a boil. Reduce heat and simmer uncovered for 15 minutes, or until potatoes are tender.

* Meanwhile, in a medium pot, melt the butter, add the flour, 2 teaspoons of salt, pepper, and mustard, stirring to make a smooth paste. Gradually stir in the milk; cook over medium heat until bubbly, stirring constantly. Add the cheese and stir until melted. Then, pour the cheese mixture into the potato mixture, and mix well. Add the parsley flakes, stewed tomatoes and their liquid; stir, and continue to cook over low heat until hot enough to serve.