In a medium bowl, whisk together the all-purpose flour, baking soda, and salt.
Cream together the peanut butter, unsalted butter, granulated sugar, and light brown sugar until well blended.
Add in the egg, milk, and vanilla extract, mixing well.
Gradually add in the dry mixture until completely blended.
Chill the dough in the refrigerator for at least one hour.
Preheat your oven to 375°F and line baking sheets with parchment paper.
Shape cookie dough into one-inch balls and roll them in granulated sugar.
Bake for seven to eight minutes until lightly golden, then press a chocolate kiss on each cookie.
Return to oven and bake for an additional two minutes.
Allow cookies to cool on baking sheet for five to ten minutes before transferring to a cooling rack.
Store cookies in an airtight container with a slice of bread for up to one week.