Preheat oven to 350 degrees.
Cream together shortening, sugar, and peanut butter. Beat in egg, vanilla, and milk.
Mix in sifted dry ingredients. Roll dough out onto surface dusted with powdered sugar.
In microwave melt chocolate chips just until melted and stir until smooth.
Spread chocolate immediately onto dough and let cool 1/2 hour.
Roll dough up jelly roll style and cut into 1/2 inch slices.
Place slices on greased cookie sheet and bake 10-12 minutes or until set but not brown.
Immediately roll cookies in powdered sugar and place on wire rack to cool completely.
When cooled, roll in powdered sugar again.