Preheat oven to 375 degrees.

Cream shortening, peanut butter, and sugars together until light and fluffy, 1-2 minutes. Add in vanilla, and eggs one at a time. In a separate bowl whisk together flour, baking soda, and salt and add to dough. Mix to combine. The dough will be very soft- that’s normal!

Roll dough into 1/2 inch (or a little larger) balls, roll in sugar, place on ungreased cookie sheet and do the little forky criss-cross thing.

Bake for 6-8 minutes, or until puffed and set, but not browned. Remove from oven, let cool on baking sheet for 2-3 minutes and then transfer to cooling rack.

Beat peanut butter, butter, sugar, and vanilla together until smooth, if needed, add milk until desired consistency is reached. When cookies are completely cooled, spread a layer of frosting on one side and sandwich together.