Preheat your oven to 375F and line a baking sheet with parchment paper. Unwrap the chocolate kiss candies and set aside.
In a large bowl, cream together the creamy peanut butter, unsalted butter, granulated sugar, and brown sugar until light and fluffy.
Beat in the egg, milk, and vanilla extract until well combined.
In a separate bowl, whisk together the gluten free all-purpose flour and baking soda, then gradually mix into the wet ingredients until a dough forms.
Roll the dough into 1-inch balls, roll each ball in extra granulated sugar if desired, and place on the prepared baking sheet.
Bake for 8-10 minutes until the cookies are lightly puffed and golden on the bottom.
Remove from the oven and immediately press a chocolate kiss candy into the center of each cookie. Let cool completely on a wire rack.