Preheat the oven to 325 degrees F. Line a baking sheet with parchment paper. Pour powdered sugar into a bowl.
In a bowl, mix together the flour and salt together. Set aside.
In a mixer, beat the butter, sugar, and vanilla together until light and fluffy.
Add in the flour mixture and beat together until the mixture comes together. It may look clumpy at first but if you press it, it should stick together.
Take about 2 tablespoons of dough and create a deep indent. Stuff a mini peanut butter cup in the middle, then cover completely with dough.
Roll into a ball, and place at least two inches apart on the baking sheet.
Bake for 13 - 15 minutes or until they just begin to brown.
Allow them to cool slightly on the baking sheet until they are just cool enough to touch.
Toss the cookies in the powdered sugar, then set aside to cool completely.