In a large mixing bowl, combine the unsalted butter and powdered sugar. Cream them together on medium speed for about 3-5 minutes until light and fluffy.

Sift the all-purpose flour into a separate bowl, then gradually add it to the butter mixture. Mix on low speed until just combined.

Finely chop the pistachios and gently fold them into the dough, ensuring an even distribution.

Divide the dough into two equal portions, shape each into a log, wrap in plastic wrap, and refrigerate for at least 2 hours.

Preheat your oven to 350°F (175°C) about 20 minutes before baking.

Slice the chilled logs into ¼-inch thick rounds and place on prepared baking sheets. Bake for 10-12 minutes until edges are lightly golden.

Remove from the oven and let cool on the baking sheet for about 5 minutes, then transfer to a wire rack to cool completely.