Cream the butter and sugar together until completely mixed. Add the cardamom and beat on a higher speed for about 1 minute. Scrape down the sides and bottom of the bowl.

Beat in the egg and vanilla until incorporated. Scrape the bowl again.

Whisk together the flour and salt. Add to the butter mixture and mix on lowest speed. When barely combined, sniff the dough. If you cannot smell the cardamom, add more, sprinkling 1/2 teaspoon at a time, until you can tell the cardamom is present. It should not be overwhelming but nor should it be undetectable. Mix just until the dough is combined. Chill for 30 minutes.

Remove dough from the fridge and shape it into a log on plastic wrap. Then roll it into a cylinder wrapped snugly with plastic wrap. A trick to help it keep its shape is to place the log inside of a slit paper towel roll, but I was out. Let it chill until firm enough to slice, probably overnight--I froze mine first.

When ready to bake, preheat the oven to 325 F. Slice the logs into 1/8-inch thick cookies and place them on parchment or silicone-lined cookie sheet. Place them about 1 1/2-2 inches apart; you will get 12 cookies to a sheet. Brush each cookie lightly with the beaten egg white. Sprinkle each cookie with finely chopped pistachios and coarse gold sprinkles. Bake for 18-20 minutes, until golden brown and crisp. Let cool on sheet.

These cookies will keep in a tin for quite some time, at least a few weeks. They are very similar to shortbread in that respect, although I have not tested it past 2 1/2 weeks yet.