Prepare ahead of time: Coarsely chop ½ c nuts. Cut 16 maraschino cherries into eighths and set aside.
Combine the ¼ c maraschino cherry juice and ¾ c milk in a one c measure. Set aside.
Beat egg whites stiffly just before the step that adds the nuts and cherries.
Preheat oven to 350°F. Generously grease and flour two 9-inch round layer cake pans and set aside.
Sift the flour, baking powder and salt together onto waxed paper or in a medium bowl; set aside.
Cream butter, shortening, and sugar in a large bowl until fluffy (about five minutes).
Add sifted dry ingredients to the creamed mixture alternately with the milk-maraschino cherry juice mixture, beginning and ending with the dry ingredients. Beat well after each addition.
Fold in nuts and cherries, then fold in the beaten egg whites.
Divide the batter between pans and bake for 30 to 35 minutes, or until springy to touch.
Cool cakes in pans on wire racks for about five minutes. Loosen carefully around edges and turn out onto the racks. Cool to room temperature.