Preheat oven to 375 degrees. Line two baking sheets with parchment paper and set aside.
Combine softened butter and peanut butter in a large bowl. Add in both sugars, then cream until like and fluffy. Next add in egg, milk, and vanilla, stir again.
To the peanut butter mixture, add in flour, baking soda, and salt. Mix until just incorporated, then scrape the sides of the bowl and mix one more time.
Scoop cookies into uniform balls (I used a 1 1/2 tablespoon cookie scoop). Roll between your hands then roll in more sugar. Place on the baking sheet.
Bake 8-10 minutes. Remove from oven then immediately place an unwrapped Hershey kiss into each cookie. Cool on the hot baking sheet for 5 minutes then transfer to a cooling rack.