In the bowl attached to your standing mixer fitted with the paddle attachment, mix the granulated sugar, brown sugar, peanut butter, butter, egg, and vanilla for 1 minute at medium-high speed.
Add the flour, baking soda, and salt and mix on low speed until the flour is incorporated, then mix at medium-high speed for another full minute.
Add the dough to a small bowl and cover it with plastic wrap. Place the dough in your fridge to rest and chill for 30 minutes. Gluten-free flour needs time to absorb the liquid, so resting the dough will net better results.
Preheat the oven to 375º F and line three baking sheets with parchment paper or silicone baking mats.
Using your hands (or wear disposable gloves), grab a small 1" piece of dough and roll it into a ball. Repeat until you have 36-38 evenly-sized balls. Roll each piece of dough in sparkling or granulated sugar, then place each cookie on your baking sheet about 2" apart.
Bake the cookies for 9-10 minutes until the bottom is lightly browned and the cookies are soft-baked. Work in batches. Immediately press an unwrapped Hershey's Kiss into the center of each hot cookie.
Allow the cookies to cool for 10 minutes on the baking sheet before transferring them to a wire rack to finish cooling.
Notes
Cracking: The cookies will lightly crack when you push the Hershey's Kiss into the center. Cracking is normal but be gentle to keep the cookie intact.Alternative to Hershey's Kisses: Instead of using Hershey's Kisses, use mini Reese's Peanut Butter Cups or any chocolate candy. See dairy-free options for other suggestions.Alternative to BRM Flour: I used Bob's Red Mill 1-to-1 Gluten-Free Flour Blend for this recipe. If using another flour blend, make sure it contains xanthan gum. If not, add 1/2 tsp of it.Alternative toPeanut Butter: Make sure to use smooth peanut butter for the best results, avoiding any peanut butter brands where the oil separates from the butter. You could use another nut butter - like almond butter - but the texture of the cookies may vary. Sunbutter is smooth and a good nut-free alternative.For a Chewier Cookie: Add one tablespoon of milk to the batter. The cookies will be chewier. They may also spread more, so chill the dough well before baking.Dairy-Free Options: Use dairy-free butter and omit Hershey's Kisses. Instead, use the backside of a tablespoon to create a small indent in the hot cookies, then fill the center with dairy-free Enjoy Life chocolate chips.Egg-Free Option: I have not tested this recipe without the egg, but if you do, I recommend using a flax egg. Combine one tablespoon of flaxseed meal with three tablespoons of warm water. Allow the mixture to sit for five minutes until it gels.Storing Cookies: Store leftover cookies in a sealed container at room temperature for 3-4 days.