Mix the butter, salt, vanilla sugar and egg yolk in a bowl using a hand mixer.
Sift the flour, add ground almonds and flour to the butter mix, and quickly knead a firm dough.
Divide the dough into quarters and form four rolls, each one about 2 to 3cm (0.78 oz 1.18 inch) thick. Cover the rolls with cling wrap and cool them for about an hour.
Flour the worktop and cut the rolls into slices (about as thick as a finger) and form little crescents.
Put the Kipferl on a greased baking sheet, or a sheet lined with parchment paper.
Bake at 160°C / 320°F in a pre-heated oven for 12 to 15 minutes.
Remove the almond crescents carefully with a palette knife.
Fill the icing sugar into a small bowl and dust the Kipferl while they are still warm.
Let the cookies cool completely on a cooling rack.
