Sift egg yolks into small bowl.

In separate bowl, sift together flour, starch and confectioners’ sugar.

Mix together butter, egg yolks, flour mixture, vanilla seeds or extract and salt until combined (do not overwork mixture).

Cut dough in half; roll out each half onto parchment paper into 1/4-inch thickness.

Cover dough and refrigerate for at least 2 hours or up to 8 hours.

Using 3-inch round cookie cutter, cut out 20 rounds from dough.

Using Christmas-shaped cookie cutters, cut out shapes from half of the rounds.

Bake in 350°F oven on baking sheets lined with parchment paper on middle rack for 8 to 10 minutes or until lightly golden.

Let cool on racks.

Fill pastry bag with Nutella^® hazelnut spread and pipe onto cookies without cutouts; top with cutout cookies, pressing gently to allow Nutella^® hazelnut spread to flow out of cutouts slightly.