Preheat your oven to 350°F and line two baking sheets with parchment paper.
While the oven is heating, unwrap the chocolate kisses and set them aside.
In a mixing bowl, use an electric mixer to cream together the butter, peanut butter, and both sugars until smooth and well combined. Add the egg and continue mixing until fully incorporated. Then mix in the flour, baking powder, vanilla extract, and salt until a soft dough forms.
Scoop about 1½ tablespoons of dough and roll into a smooth ball. Coat each dough ball evenly in sugar.
Place the coated dough balls on the prepared baking sheets, spacing them a couple of inches apart.
Bake on the middle rack for about 12 minutes, or until the bottoms are lightly golden. Immediately press a chocolate kiss into the center of each cookie while they are still hot.
Transfer cookies to a cooling rack and allow them to cool completely before serving.