1. In a medium bowl, combine butter and sugar; cream together until light and fluffy. Beat in egg yolks. Add flour, cardamom, salt and zest; blend until dough is evenly mixed. Adjust cardamom to taste.

2. Divide dough in four balls on sheets of plastic wrap, and flatten each into a disk. Wrap tightly, and chill for at least 1 hr. or overnight.

3. Preheat oven to 350°F and line baking sheets with parchment paper or butter them.

4. Take 1 ball of dough from refrigerator. (Keep remaining dough chilled.) On a lightly floured surface with a lightly floured rolling pin, roll dough out to 1/8- to ¼-in. thickness. Cut into shapes and place on prepared baking sheets.

5. Bake until bottoms just begin to brown, 8 to 10 min. Transfer to wire rack to cool completely. Continue to roll, cut and bake remaining dough.

6. For the icing, combine butter, sugar, salt and vanilla in a mixing bowl. Beat at low speed, gradually adding juice to reach desired consistency. Decorate completely cooled cookies as desired.

*Use large, granular-type cane sugars; in particular, large crystal Turbinado sugar or Demerara.
**Cardamom can be found in the spice section of most grocery stores