Beat the soft butter with the powdered sugar, salt and cardamom until frothy and soft.
Stir in the egg yolks and then fold in the flour and cornstarch. If the dough is still too sticky, knead in a little more flour. The dough should be soft but not overly sticky in consistency. Wrap the dough in cling film and refrigerate for at least an hour.
Shape the dough into balls of the same size with a diameter of about 2 cm, place them on a baking sheet lined with baking paper and flatten them lightly.
Bake on the middle shelf for about 12-15 minutes, until the edge is slightly golden brown.
Finally, toss the still warm thalers in powdered sugar.