Beat the egg whites until stiff. Cream together the butter and sugar and add the beaten egg yolks. Dissolve the soda in the sour milk and add alternately with the sifted dry ingredients to the above mixture. Fold in the egg whites, then the raisins and nuts. Bake in muffin tins for about 30 minutes in a 350 degrees F oven. Frost with Seven-Minute frosting.