Preheat oven to 350 degrees
Cream together sugar with the butter and shortening..
Add eggs beating well, add vanilla and dry ingredients and beat together.
Bake for 9-12 minutes until done but soft.
FILLING:
Beat egg whites (reserving yolks for another recipe) then once fluffy add vanilla and milk.
Beat in powdered sugar, shortening and flour.
Beat until light and frosting like.
Once cookies are cool frost one and sandwich with another one