Combine butter, peanut butter, sugar and brown sugar in a large bowl and beat until fluffy.
Add egg, milk and vanilla to the mixture. Mix well.
In a second bowl, combine dry ingredients including flour, baking powder, salt and soda.
Gradually add dry ingredients to the wet ingredients.
Chill batter for one hour. This makes the dough easier to handle.
Preheat oven to 375 F.
Unwrap the Hershey kisses.
Add the sugar for decoration to a bowl.
Shape dough into 1-inch balls. Roll in sugar. Place about 2 inches apart on un-greased cookie sheets. We use silpat cookie sheet mats to make clean up easier.
Bake for 10-12 minutes or until edges are firm. As you pull the cookies from the oven, carefully press a Hershey kiss into the center of each.
Cookies should cool overnight or for an hour in the refrigerator before stacking them for storage.