Step 1

Whisk flour, pumpkin pie spice, salt, and baking soda together in a bowl until combined.

Step 2

Beat butter in a large bowl with an electric mixer until smooth and creamy. Add 1/2 cup plus 2 tablespoons powdered sugar and beat until smooth. Mix in pumpkin puree and vanilla extract. Beat on medium- high speed until completely incorporated. Add 1/2 of the flour mixture, mixing until just combined. Add remaining flour mixture and mix until just combined.

Step 3

Cover bowl and refrigerate dough until chilled, about 1 hour.

Step 4

Preheat the oven to 350 degrees F (175 degrees C). Line 2 baking sheets with parchment paper.

Step 5

Roll out dough to 1/4-inch thickness on a lightly floured surface. Using a pizza cutter or pastry wheel, cut dough into 1x2-inch rectangles. Use the back of a bamboo skewer to poke 3 holes into each cookie. Place cookies 1/2 inch apart on the prepared baking sheets. Sprinkle each cookie with white sugar.

Step 6

Bake in the preheated oven until cookies are lightly browned, 10 to 15 minutes. Cool shortbread on the baking sheet for a few minutes before transferring to a wire rack to cool completely.