Cream shortening in a large mixing bowl; gradually add sugar, beating well. Add egg, milk, and vanilla; beat well. Stir in peanut butter.
Combine flour, soda, and salt in a medium mixing bowl; add to peanut butter mixture, stirring well. Shape into 1-inch balls. Roll in additional sugar, and place 2 inches apart on ungreased cookie sheets.
Bake at 375° for 10 minutes. Remove from oven; firmly press a candy kiss in center of each cookie. Remove to wire racks to cool.