Easy-to-make Pistachio Shortbread Cookies are delicately sweet and studded with bits of salty pistachios. And for an extra-special touch, fill them with lemon curd, fruity jam, or Nutella to turn them into sandwich cookies!
Add butter, powdered sugar, and salt to the bowl of a large food processor. Process until smooth (about eight 1-second pulses). Add flour and pulse until mixture looks crumbly and chunky (about six 1-second pulses). Add pistachios and quickly pulse about 4 more times so that the pistachios are incorporated but not further chopped.
Turn the dough out onto a work surface and shape into a rough ball. Cut ball in half and form each piece of dough into an 8-inch long log. Tightly wrap each log in plastic wrap and freeze for 30 minutes.
Preheat oven to 350°F. Line two baking sheets with parchment paper. Remove one log of dough from the freezer. Cut dough into 1/4-inch thick slices, rolling log every few slices to maintain the round shape of the cookies. Arrange cookies on lined baking sheet. Bake until cookies just barely turn a light golden color around the edges, between 10 and 15 minutes. Allow to cool on baking sheets.
Repeat steps with the second log of cookie dough. Once cookies are completely cool, store in an airtight container.
You may use unsalted pistachios, if you prefer (or if that's all you can find).
To achieve round logs of dough, I shape them the best I can and then lightly roll them on the counter like a rolling pin after they're wrapped in plastic wrap.
While the first sheet of cookies is baking, take the second log of cookie dough out of the freezer, slice it, and arrange cookies on second cookie sheet so that it's ready to pop in the oven as soon as the first sheet comes out.
If desired, once cookies are completely cool, you may make sandwich cookies by spreading 1/2 teaspoon of lemon curd, jam, or Nutella on one cookie and topping with another cookie.