1. Grease cookie sheet or line it with parchment paper; set aside.
2. In a large mixing bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add sugar. Beat mixture until combined, scraping sides of bowl occasionally. Beat in egg yolks and vanilla. Beat in as much of the flour as your can with the mixer. Stir in any remaining flour. Cover; chill about 1 hour or until dough is easy to handle.
3. Preheat oven to 375 degrees F. Shape dough into 1-inch balls. Roll balls in egg whites then roll in chopped macadamia nuts. Place balls 1 inch apart on prepared cookie sheet.
4. Bake in preheated oven about 10 minutes or until bottoms are lightly browned. Transfer to a wire rack and let cool. Spread Vanilla Cream Icing on tops of cookies. If desired, sprinkle frosted cookies with cardamom. Makes about 5 dozen cookies.
5. Vanilla Cream Icing: In a medium mixing bowl, beat 1/4 cup butter, softened; one 3-ounce package cream cheese, softened; and 1/2 teaspoon vanilla with an electric mixer on medium speed until smooth. Gradually beat in 2 cups powdered sugar until smooth and icing is of spreading consistency.
TO STORE: Place cookies in single layer in an airtight container; cover. Store in the refrigerator for up to 3 days. Or freeze unfrosted cookies for up to 3 months; thaw and frost.