Preheat the oven to 375°F. Spray a mini muffin tin with nonstick spray. Set aside.
In a medium bowl, combine the flour, baking soda, and salt. Set aside.
1½ cups all-purpose flour, ½ teaspoon baking soda, ¼ teaspoon kosher salt
In a large bowl, using a hand mixer, combine the butter, sugar, and brown sugar, mixing on medium speed until they are combined. Add in the egg, vanilla, and peanut butter, and continue to mix on medium speed until the mixture resembles wet sand.
½ cup unsalted butter, ½ cup granulated sugar, ½ cup brown sugar, 1 large egg, 1 teaspoon pure vanilla extract, ½ cup creamy peanut butter
Add the flour mixture in 2 batches, slowing mixing to combine the flour into the dough. Use a rubber spatula and scrape the sides of the bowl if necessary.
Scoop the dough into 1½-inch balls of dough into the prepared mini muffin tin.
Bake for about 9-11 minutes, until the cookies begin to turn golden brown. Remove from the oven and quickly add a peanut butter cup to the center of each cookie and press down. Repeat until all of the cookies are done.
24 mini peanut butter cups
Remove cookies from pan and allow to cool.