In a medium bowl, whisk together the gluten-free flour, baking soda and salt. Set aside.
In the bowl of a stand mixer, or using a hand mixer, beat the butter for 1 minute until creamy.
Add the brown sugar and granulated sugar and mix until creamed, about 2-3 minutes.
Add the egg, peanut butter and vanilla and beat until creamy and smooth, another minute or so. Scrape down the sides and bottom of the bowl.
With the mixer running on low, slowly add the dry ingredients to the wet ingredients and mix until well-combined.
Cover the bowl and refrigerate for at least 1 hour, or up to 3 days.
Preheat the oven to 350°F. Line large baking sheets with parchment paper or silicone baking mats.
Place the unwrapped chocolate kiss candies in a bowl and set them in the freezer.
Scoop the cookie dough into round balls, 1 tablespoon per ball. (Don't make them too big or you won't have the right cookie-to-chocolate ratio.) Roll each ball in granulated sugar before placing it on the baking sheet, about 2 inches apart.
Bake for 10-12 minutes or until the tops crack slightly.
Remove from the oven and immediately press a chocolate kiss candy into each cookie.
Let cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.