Diva's Grandma Sarah's Whoopie Pie Cookies

Diva’s Memories of Recipes Whoopie Pie Cookies
Inspiration:  This is marked in one of Grandma Sarah's recipe books from 1965.  I love when she circled recipes. Most are wonderfully delish!
Ingredients: 1 cup shortening 1 cup sugar 2 eggs, beaten 5 cups flour 3/4 cup cocoa 1~1/2 tsp salt 1 cup sour milk 2 tsp baking soda 1 cup hot water ____________ filling: 2 egg whites, beaten 1 TB vanilla 4 TB milk 4 cups powdered sugar 1 cup shortening	Instructions: Cream shortening and sugar; add eggs.  Add sifted dry ingredients alternating with sour milk. Combine soda and hot water; add.  Drop from TB spoon onto cookie sheet and Bake @ 400 degrees F for 10-15 minutes. ____________ filling: Beat egg whites, vanilla and milk.  Add 2 cups powdered sugar.  Cream 2 cups powdered sugar and shortening together. Mix both together.  Spread between cookies when they are cooled.
Variation:  if you don't have sour milk, you can add 1 TB vinegar to the milk. I have also substituted peanut butter for the shortening in the filling.