1/2 c. butter
1/2 c. chopped onion
1 tbsp. salt
4-5 c. sliced raw potatoes
1 1/2 - 2 c. water
2 tbsp. parsley flakes
2 c. hot milk
1 egg yolk, slightly beaten in 1/2 c. cold milk
1/8 tsp. black pepper
Pinch of cayenne

Melt butter in heavy saucepan over low heat. Add onion and cook slowly, but do not brown. Add salt, potatoes and water. Cover and cook slowly often stirring until potatoes are tender (about 30 minutes). Combine hot milk with egg yolk and cold milk and gradually add to hot soup. Add pepper and garnish with parsley flakes.