Preheat your oven to 375°F (190°C).
In a large mixing bowl, cream together the softened butter, peanut butter, granulated sugar, brown sugar, egg, and vanilla until smooth and well combined.
Add the all-purpose flour and baking soda to the bowl, stirring until the dry ingredients are fully incorporated into the dough.
Roll about a tablespoon of the cookie dough into a ball using your hands. Place the dough balls on an ungreased baking sheet, leaving some space between each cookie.
Bake the cookies in the preheated oven for 8-10 minutes, or until the edges are slightly golden.
As soon as the cookies come out of the oven, gently press a Hershey Kiss into the center of each warm cookie, making sure it sticks to the cookie.
Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.