Measure out all your ingredients and ensure the butter is softened to room temperature—this is crucial for creating a smooth, cohesive dough. Add the flour, sugar, salt, and finely chopped pistachios to a food processor. Pulse for 1 to 2 minutes until the pistachios are ground into small, evenly distributed pieces throughout the flour mixture. I like to use finely chopped pistachios rather than whole ones because they incorporate more uniformly and create a more refined texture in the finished cookie.

Add the softened butter and vanilla extract to the food processor with the dry mixture from Step 1. Pulse until the ingredients come together into a cohesive dough—this should take just a minute or two. The dough will be slightly crumbly at first, then will pull together as you process. Transfer the dough to a clean work surface and gently knead it once or twice by hand to ensure everything is evenly combined, then shape it into a 2-inch by 10-inch log.

Wrap the dough log tightly in plastic wrap or parchment paper and place it in the refrigerator for at least 2 hours. This chilling time is essential—it allows the butter to firm up so the cookies will hold their shape during baking, and it also allows the flavors to meld together. You can prepare the dough up to a day ahead if needed.

While the dough is chilling, preheat your oven to 325°F and line two baking sheets with parchment paper. Starting your oven early ensures it reaches the proper temperature by the time your cookies are ready to bake.

Remove the chilled dough from the refrigerator and slice it into 1/2-inch thick coins using a sharp knife—a gentle sawing motion works better than pressing down, which can crack the dough. Arrange the cookies on your prepared baking sheets about 2 inches apart. Brush the top of each cookie lightly with water using a pastry brush, then sprinkle with sanding sugar for sparkle and crunch. I find that the water helps the sugar adhere beautifully and creates a lovely crystalline topping. Bake for 15 to 18 minutes until the edges are just beginning to turn light golden—the centers should still look slightly underbaked when you remove them from the oven.

Allow the cookies to rest on the baking sheet for 5 minutes—this brief rest period allows them to set and firm up slightly without becoming hard. Transfer the cookies to a wire rack to cool completely. These shortbread cookies will continue to firm up as they cool, developing their characteristic tender, buttery crumb.