Alfredo Sauce
["1/2 c. Parmesan cheese", "2/3 c. sour cream", "1/4 lb. butter", "1 egg yolk"]
["Beat egg yolk lightly; add yolk to sour cream.", "Melt butter on top of stove in a saucepan.", "Add sour cream mixture to melted butter.", "Add Parmesan cheese and heat thoroughly.", "Do not burn. Pour mixture over cooked pasta."]
["Parmesan cheese", "sour cream", "butter", "egg yolk"]