Step 1

Stir together 2 teaspoons of the sugar and the pistachios in a small bowl.

Step 2

Put butter and remaining sugar into the bowl on an electric mixer fitted with paddle attachment. Mix on medium speed until combined. Add egg yolk and vanilla; beat until pale and fluffy, about 2 minutes. Reduce speed to low. Add flour, cardamom, saffron, and salt. Mix until just smooth. Wrap dough in plastic and refrigerate until firm, about 2 hours.

Step 3

Sprinkle a flat work surface lightly with flour. Transfer the dough to the prepared surface. With a floured rolling pin, roll out a rectangle about 1/8 inch thick. Use a 2-inch square cookie cutter to cut about 16 squares. You can also use a knife or a pizza wheel. Re-roll any scraps, and cut one more time before discarding any remaining dough.

Step 4

Carefully transfer the cut pieces to two baking sheets lined with silicone mats or parchment paper, leaving a little space between each square. Chill until firm, about 30 minutes.

Step 5

Preheat oven to 350°F. Remove the trays from the fridge. Brush each cookie with egg white. Sprinkle with the pistachio mixture and a little sea salt.

Step 6

Bake until firm and edges are pale golden brown, 10 to 12 minutes. Transfer to a wire rack to cool. Cookies can be stored in an airtight container at room temperature for up to 3 days.