Preheat oven to 350 degrees

Prepare 2 cookie sheets. Let the butter soften until it is malleable. Beat the butter, egg yolk and sugar until light and creamy, then beat in the salt, cardamom and flour. The dough will be very buttery at this point. Shape the dough into 4 cylinders, each about 1 inch in diameter and 6 inches long. Wrap the cylinders in wax paper and chill for at least 2 hours. Slice the cylinders into ¼-inch rounds and transfer them to cookie sheets. Top each cookie with a sprinkling of almonds and lightly brush the nuts with egg white. Bake for 12 minutes. Cool on a cookie rack. Store in an airtight container.