Line two 24-count mini muffin pans with mini liners (the second pan will need only 12 liners since this recipe makes 36 cups). Set aside.
With a handheld or stand mixer fitted with a paddle attachment, beat ½ cup (129g) of the peanut butter, butter, confectioners’ sugar, and salt on medium speed in a medium-size bowl until thick and smooth, about 3 minutes. You