Beer-Cheese Chowder Soup

3 cups diced, peeled, potatoes
3/4 cup finely chopped onions
1/2 cup chopped celery
2 1/2 cups water
1/4 cup margarine or butter
1/2 tsp dry mustard
1 1/2 tsp salt
1/4 cup flour
1/4 tsp pepper
1 cup or 1 12 oz beer (depending on taste)
1 cup milk (Beer can be omitted-just use 2 cups of milk)
1 1/2 tsp Worcestershire Sauce
6 oz (3/4 cup) cubed process cheese (I use sliced American cheese)
6 oz. grated cheddar cheese
1 16 oz can tomatoes, undrained, cut up (or 1 chopped fresh tomato)
1 TBS finely chopped fresh parsley

In large pan, combine potatoes, onions, celery and water. Bring to boil. Redue heat; cover and simmer 15-20 minutes until potatoes are tender. In a medium saucepan, melt margarine. Stir in flour, salt mustard and pepper. Cook 1 minute, stirring constantly, until smooth and bubbly. Gradually stir in beer and milk. Add Worcestershire sauce. Cook until thickened, stirring constantly. Add cheeses; stir until melted. Blend into the potato mixture. Stir in tomatoes and add parsley. Heat gently, stirring frequently, but do not boil. Makes 6-8 servings.