The Best Homemade Chocolate Chip Cookies

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.

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

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.

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

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.

Spread frosting over cooled cookies.