Preheat your oven to 375°F (190°C) and line a cookie sheet with parchment paper or a silicone baking mat.
Using a mixer, blend together the peanut butter, butter, white sugar, and brown sugar until well combined.You will want to mix it for a couple of minutes so it gets nice and fluffy and light in color.
Next, add the egg, milk, and vanilla, and beat until the mixture is smooth and fully incorporated.
In a separate bowl, combine the flour, baking powder, and salt.
Gradually add the dry flour mixture to the peanut butter mixture, mixing until a dough forms.
Roll the dough into tablespoon-sized balls and then roll into sugar. Place your cookie dough balls on your prepped cookie sheets. Ensure there's about 2 inches of space between each cookie.
Bake the cookies at 375°F (190°C) for 7-9 minutes. Be cautious not to overcook; these cookies are best when they are soft and just cooked through.
As soon as you take the cookies out of the oven, gently press a Hershey's Kiss into the center of each one.
Allow the cookies to cool, giving the chocolate time to set, before serving.
Enjoy!