Preheat oven to 350°F. Line two baking sheets with parchment paper or a baking mat and set aside.
Cream butter and sugars. Add peanut butter and blend until smooth. Add egg, milk and vanilla.
Next add the flour, baking soda and salt. Mix just until combined. Refrigerate 10-20 minutes if the dough is too sticky to handle.
Roll dough into 1″ balls (I use a full small cookie scoop). Roll in sugar and then place onto prepared baking sheet.
Bake for 7-9 minutes or until very lightly browned on the bottoms.
Press Hershey's kiss into cookie immediately after the cookies comes out of the oven. If the cookies have cooled slightly, put the cookies back in the oven for 1 minute once the kisses are on top to ensure they stay on top of the cookie.