In a medium bowl, whisk together the flour, baking soda, and salt together. Set aside.
1 ½ cups all-purpose flour, ¾ teaspoon baking soda, ½ teaspoon salt
Using a hand mixer or stand mixer, beat the butter and peanut butter together until creamy, about 1 to 2 minutes.
½ cup unsalted butter, ⅔ cup creamy peanut butter
Add brown sugar and 1/4 cup granulated sugar and mix on medium speed until creamy and smooth, scraping down the sides of the bowl as needed.
¼ cup granulated sugar, ½ cup packed light brown sugar
Add the egg and beat on high until completely combined and incorporated.
1 egg
Add the vanilla extract and milk and mix until combined.
1 teaspoon vanilla extract, 1 tablespoon milk
Add the dry ingredients to the wet ingredients and mix on low just until combined.
Cover and chill the dough for 1 hour. (If you need to chill the dough for longer, you may need to let the dough sit at room temperature for 15 minutes or so until the dough softens enough that it can be scooped.)
Preheat the oven to 350°F. Line two large baking sheets (half sheets) with silicone baking mats or parchment paper and set aside. Place remaining 1/2 cup of granulated sugar in a small bowl.
Use a small cookie scoop or spoon to scoop about 1 tablespoon of cookie dough and roll into a ball with the palms of your hands. Roll the ball in the sugar and place on the prepared baking sheet about 2 inches apart. Repeat with remaining cookie dough.
½ cup granulated sugar
Bake for 8 to 10 minutes or until the tops of the cookies begin to shows small cracks. The cookies should not brown at all. Remove cookies from the oven and allow to cool for 5 minutes.
Gently press a kiss into the center of each cookie. Let cookies sit on baking sheet for another 5 to 10 minutes before carefully moving to a wire rack to cool.
30 to 36 Hershey's Kisses