In a mixing bowl, cream the softened butter until light and fluffy.
Gradually add the icing sugar to the creamed butter and mix until well combined.
Stir in the pure vanilla extract to infuse a delightful flavor into the mixture.
In a separate bowl, whisk together the all-purpose flour and cornstarch. Gradually add this dry mixture to the butter mixture, mixing until a soft dough forms.
Gently fold in the chopped mini peanut butter cups into the dough until they are evenly distributed.
Take spoonfuls of the dough and shape them into rounds or your desired cookie shape. You can use a cookie scoop for consistent sizing.
Place the shaped cookies on a baking sheet lined with parchment paper, leaving space between each cookie.