Aunt Sally Cookies

Step 1
Make cookies: Cream together shortening and sugar in a large bowl until smooth. Beat in molasses and egg yolks until well combined. Mix together flour, baking soda, cinnamon, ginger, cream of tartar, and salt in a separate bowl. Mix into molasses mixture in batches, alternating with sour milk, beating briefly after each addition. Cover dough and chill in the refrigerator for 30 minutes.

Step 2
Preheat the oven to 350 degrees F (175 degrees C).

Step 3
Roll dough out to 1/8-inch thickness on a lightly floured surface. Cut into rectangular shapes (I like to use a Spam can). Place cookies 1 inch apart onto an ungreased baking sheet.

Step 4
Bake in the preheated oven until lightly browned, 8 to 10 minutes. Transfer cookies to wire racks to cool completely.

Step 5
Make frosting: Combine marshmallows, sugar, water, and vinegar in a large bowl. Place the bowl over a pot of simmering water, stirring occasionally, until marshmallows melt. Carefully remove the bowl from heat, add egg whites, and beat with an electric mixer until shiny and fluffy, about 7 minutes. Stir in confectioners' sugar and vanilla until well blended.

Step 6
Spread frosting over cooled cookies.