Cream butter, sugar and vanilla together until fluffy. Sift flour, baking powder and salt together. Add milk alternately with flour to creamed mixture. Beat until smooth. Fold in nuts and beaten egg whites. Pour into 2 greased 8" square baking pans. Bake @ 350 degrees 35 minutes. Cool. Just before serving, put layers together with and frost with unsweetened whipped cream; sprinkle with nuts.