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 the top no longer looks dough (do not let the bottoms brown or the cookies will be dry instead of soft. Remove from oven and let sit on the pan for a couple minutes.
Press Hershey's kiss into cookie about a minute after the cookies come 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.
Recipe slightly adapted from Hershey's.Recipe change (9/16/20): I reduced the flour by 1/4 cup to create less cracking. If your dough is too sticky, try adding 1-3 Tablespoons extra flour.