Prepare the Oven: Preheat the oven to 375°F and line the cookie sheets with parchment paper.
Cream the Peanut Butter Mixture: In a large mixing bowl, or in the bowl of a stand mixer fitted with the paddle attachment, combine the peanut butter, softened unsalted butter, granulated sugar, light brown sugar, and salt. Beat on medium speed until the mixture is well combined and creamy. Add the Wet Ingredients: Add the room-temperature egg and vanilla extract to the peanut butter mixture. Beat until everything is thoroughly incorporated, then scrape down the sides of the bowl.
Finish the Dough: Add the all-purpose flour and baking soda. Mix on low speed just until the ingredients are combined. Avoid mixing beyond this point.
Shape the Cookies: Scoop portions of dough and roll them into 1-inch balls. If desired, roll each ball in additional granulated sugar to coat the outside.
Arrange the Dough: Place the sugared dough balls on the prepared cookie sheets, leaving 2 inches of space between each one.
Bake the Cookies: Bake for 8–10 minutes, or until the cookies appear puffy and cracked and the bottoms have just started to turn brown.
Add the Chocolate Kisses: Immediately after removing the cookies from the oven, press one unwrapped chocolate kiss into the center of each cookie. The warm cookies will crack around the chocolate, which is completely fine.
Cool Completely: Leave the cookies on the baking sheet until they have cooled completely and the chocolate has set.
Store the Cookies: Serve once cooled, or transfer the cookies to an airtight container and store for up to 1 week.