Preheat oven to 375 degrees. Line two baking sheets with parchment paper and set aside.
Beat softened butter and peanut butter in large bowl until well blended. Measure and add in 1/3 cup granulated sugar and brown sugar. Stir until light and fluffy. Add egg, milk, and vanilla; stir well.
Stir flour, baking soda and salt into peanut butter mixture until just incorporated. Scrape the sides of the bowl and mix again briefly.
Scoop into cookies using a 1 1/2 tablespoon scoop. Roll in between your palms and then roll in sugar. Place on baking sheets.
Bake 8-10 minutes or until very lightly golden in color. Remove from oven and immediately press a Hershey kiss into each cookie. Cookies will crack around the edges with you press the chocolate in...totally normal! Cool 5 minutes on the hot baking sheet and then remove to cooling racks.
Store cooled cookies in airtight containers for up to three days.
*Recipe based off the Hershey Kiss package around the holidays.