Chop bacon fine and fry in a skillet until crisp and brown. Put the cooked bacon in a large saucepan and add potatoes, onion, celery, salt, and pepper. Cover with water and cook until vegetables are tender, about 25 minutes. Dribble the rivels into gently boiling soup, stirring constantly so they stay separate. Add milk and butter and cook 10 to 15 minutes more, or until rivels are done.
Rivels are little homemade egg noodles. They are good in beef and chicken stew, as well as in vegetable soups:
Pour 1 cup flour on a flat surface such as a cutting board. Make a well in the center, then pour in a slightly beaten egg to which 1 teaspoon salt has been added. Using your hands and a knife, work these 3 ingredients together into a noodle-type pastry. Knead once or twice, then chop it into small pea-size pieces.