Step 1

In a medium bowl with an electric mixer, beat butter, 1/2 cup confectioners' sugar, the egg yolk, cognac (if desired), and vanilla; mix until fluffy.

Step 2

In a medium bowl, stir together flour, baking powder, walnuts, and salt. Slowly, add flour mixture to butter mixture; mix well; but don't overmix. Cover and set aside at room temperature for 1 hour to allow dough to rise.

Step 3

Preheat oven to 350 degrees F. Coat baking sheets with cooking spray.

Step 4

Roll dough into 1-inch balls, then place on baking sheet. Bake 16 to 18 minutes or until lightly golden. Immediately sprinkle or lightly brush with orange liqueur.

Step 5

Place remaining confectioners' sugar in a resealable plastic storage bag; add a few cookies at a time and shake until completely coated. Place on wire racks to cool completely. Store in an airtight container until ready to serve.