Preheat oven to 400 degrees F. Mix the butter, confectioners' sugar, and egg yolk together with your hands. Add the flour and vanilla sugar and knead to a firm dough. Chill for about 2 hours. Roll out the dough on a floured surface until about 1/4-inch thick. Cut out about 40 Christmas shapes such as stars, bells, Santa Claus, angels, holly heaves, etc., either freehand or with the appropriate cookie cutters. Place the cookies on baking sheets lined with non-stick baking parchment, brush with the egg glaze and sprinkle with nuts. Bake for 8 to 10 minutes or until lightly colored. Leave cookies on cookie sheets for 5 minutes after removing from oven. Remove to cool on wire cake racks to cool.

Note: Make vanilla sugar by keeping a vanilla bean pod in a jar of superfine sugar. Use as needed.

A Little Book of Viennese Pastries, by Jeni Wright, Chronicle Books, 1995