95 grams or ¾ cup shelled or slivered raw pistachios, almonds, hazelnuts or walnuts
40 grams or ⅓ cup icing sugar, plus more for dusting (optional)
115 grams or ½ cup unsalted butter
½ teaspoon kosher salt
95 grams or ¾ cups all-purpose flour
Nonstick spray or softened butter, for greasing
Heat oven to 350 degrees.
Process pistachios in a food processor until finely ground. Remove 2 tablespoons and set aside.
Add icing sugar, butter and salt and pulse until well combined. Add flour and process until a slightly sticky dough forms (if your food processor is having trouble here, just dump dough out onto a counter or a bowl and mix by hand until no dry spots remain).
Lightly grease a 9-inch springform pan or tart pan with a removable bottom with nonstick spray or softened butter and line the bottom with a circle of parchment paper.
Press dough into the pan into an even layer (you can use your hands or use the bottom of a measuring cup to press dough into an even layer). Dust with icing sugar and sprinkle with reserved 2 tablespoons ground or slivered pistachios and flaky salt.
Bake until the shortbread is just golden around the edges and dough is baked through, 17 to 22 minutes.
Once the shortbread is out of the oven, remove from springform or tart pan. Dust with more icing sugar if you like. Before it cools, slice the shortbread into 24 thin wedges (start by cutting the circle into quarters, then slice each quarter in half, then each half into thirds to get nice, thin triangles.
Let the shortbread cool completely before transferring them (they will be soft and easily broken if moved before cooled).
Shortbread can be made two days ahead, wrapped tightly in plastic wrap or stored in an airtight container at room temperature. These can also be rolled into balls or crescents and baked like a traditional Mexican wedding cookie if you like.