Black Walnut Cake
["1/2 c. butter", "2 c. brown sugar", "3 egg yolks, beaten", "2 c. flour", "3 tsp. baking powder", "1/2 tsp. salt", "2/3 c. milk", "1 tsp. vanilla", "1 c. black walnuts, chopped fine", "3 egg whites"]
["Cream butter.", "Add brown sugar; beat well.", "Combine dry ingredients; add to mixture.", "Add vanilla and walnuts.", "Mix well. Fold in stiffly beaten egg whites.", "Bake in tube pan (greased and floured) at 350\u00b0 for 45 minutes."]
["butter", "brown sugar", "egg yolks", "flour", "baking powder", "salt", "milk", "vanilla", "black walnuts", "egg whites"]