Southern Moon Pies

Cookie Crusts
1/2 cup butter, softened
1 cup granulated sugar
1 egg
1 cup evaporated milk
1 teaspoon vanilla extract
2 cups all-purpose flour
1/2 teaspoon salt
1/2 cup unsweetened cocoa powder
1 1/2 teaspoons baking soda
1/2 teaspoon baking powder

Marshmallow Filling
1/2 cup butter, softened
1 cup confectioners' sugar
1/2 teaspoon vanilla extract
1 cup Marshmallow Cr