Cream butter and sugar white and fluffy. Add the flour and egg yolk and mix this quickly into the dough. Roll dough into finger thick sausages and cut them into about 6 cm long sticks.
 Roll the sticks first in egg white and then in a mixture of sugar and cinnamon. Bake for about 10 minutes at 355° F / 180° C, in the middle of the oven.
NOTE! icing sugar should not be replaced with sugar, then the dough will not stick together.