Hearty Potato Soup
["6 medium potatoes, peeled and sliced", "2 carrots, diced", "6 celery stalks, diced", "2 qt. water", "1 chopped onion", "6 Tbsp. butter", "6 Tbsp. flour", "1 tsp. salt", "1/2 tsp. pepper", "1 1/2 c. milk"]
["In a large kettle, cook potatoes, carrots and celery in water until tender.", "Drain, reserving liquid, and set aside."]
["potatoes", "carrots", "celery stalks", "water", "onion", "butter", "flour", "salt", "pepper", "milk"]