Silver White Layer Cake

Sift together 2-1/2 cup cake flour, 1-1/2 cup sugar, 3-1/2 tsp baking powder and ¾ tsp salt.  Add ½ cup shortening, 2/3 cup milk and 1-1/2 tsp flavoring.  Beat for 2 minutes on medium speed.  Add 1/3 cup milk and 4 unbeaten egg whites.  Beat 2 minutes more.  Bake 30 to 35 minutes for 8” layers or 35 to 45 minutes for 9x9” square.