Whisk together flour, pumpkin pie spice and salt until blended; set aside. In separate bowl and using electric mixer, beat together butter and sugar until light and fluffy; beat in vanilla. Stir in flour mixture just until combined. Stir in chopped TWIX® Minis. Pat dough into disk; wrap in plastic wrap and refrigerate for at least 30 minutes.
Preheat oven to 325°F. On lightly floured surface, roll out dough into 1/4-inch thickness. Cut into six 2-inch squares. Reserve remaining dough for another use.
Place cookies on parchment paper–lined baking sheet, spacing at least 2 inches apart; refrigerate for 10 minutes before baking.
Bake for 8 to 10 minutes or until bottoms are lightly golden and tops are set. Transfer to rack and let cool completely.
Tip: Roll remaining dough into 1/2-inch balls and flatten with fork for mini shortbread buttons.