Preheat the oven to 350°F. Line a cookie sheet with parchment paper, a silicone mat, or spray it with cooking spray.
In a medium bowl, microwave the butter (2 tablespoons) in 5 second intervals until it softens. Softened butter should still feel cool to the touch. Your finger should make an indent but not slide off the stick. In my microwave this only takes 5-10 seconds for a half stick of butter.
Add the peanut butter (3 tablespoons), sugar (1 tablespoon), and brown sugar (2 tablespoons) to the bowl. Use a hand mixer to beat until the ingredients are homogenous and smooth, about 2 minutes. You'll notice that the mixture lightens in color as you mix.
We are going to add the egg next, but since this is such a small recipe you only need 1 tablespoon of the egg. Here's the easiest way to do that: crack your egg into a separate small bowl. Using a fork, whisk the egg really, really well, like for at least 30 seconds. Carefully measure out 1 tablespoon and add it to the bowl with the peanut butter mixture. If it's hard to get the egg to fill a whole tablespoon, you can measure out 3 teaspoons instead.
Add the vanilla extract (½ teaspoon) to the bowl with the egg and peanut butter mixture and use your hand mixture to beat until you don't see any streaks of egg or vanilla.
Add the flour (5 tablespoons), baking powder (⅛ teaspoon), and a pinch of salt (about half of ⅛ teaspoon) to the bowl. Use a rubber spatula or wooden spoon to slowly mix until everything comes together as a dough.
Add your remaining sugar (1 tablespoon) to a very small bowl. Measure out 1 tablespoon of your dough and roll it into a ball. Roll the ball around in the sugar until the whole ball is covered in sugar.
Place the dough on your prepared baking sheet and repeat with the rest of the dough.
Bake at 350°F for 8-10 minutes.
While the cookies are in the oven, unwrap the chocolate kisses. You'll need to put them on top of the cookies as soon as you take them out of the oven.
You'll know the cookies are done when the tops look dry and the edges just start to get golden brown. The cookies will not flatten out very much in the oven, but that's ok because you want them to be thick enough to hold your chocolate kiss.
As soon as you take your cookies out of the oven, place a chocolate kiss in the center of each cookie and push it in to the flatten the cookie. The sides of the cookie will likely crack.
Leave the cookies on the hot pan for 3-5 minutes and then enjoy!