Cream the butter and sugars until light and fluffy, then beat in the egg yolk.
Stir in the cardamom, salt, and flour.
Divide the dough in two, roughly shape each piece into a log about 1 inch thick, then roll in plastic wrap or wax paper. Pull each log through you thumb and first finger to make it even and, if you prefer, longer and narrower.
Refrigerate until firm or freeze until ready to use.
Preheat oven to 375°F
Cut the dough into 1/4-inch rounds or diagonals and set themon cookie sheets at least 1 inch apart.
Bake until pale golden on top and lightly browned around the edges, 8 to 10 minutes.
Cool. Serve plain or dusted with confectioner's sugar.
Note: Time to Make does not include the time to chill the dough.