Nuts for this cookie it is possible to take any. I took a little hazelnut, almond and walnut.

Nuts grind in a blender, not too fine.

In the container combine the egg yolks, vinegar and half of the powdered sugar. Beat with a mixer, gradually adding powdered sugar. "Dough" should be thick and viscous.

Add walnuts.

Stir.

Protiven grease with vegetable oil or covered with baking paper, paper I also recommend that you lubricate with oil, to make it easier to separate the cookies. Spread the dough with a spoon (or pastry bag with a large round nozzle). The dough will spread a bit, but in the oven to cure and harden. Dried cookies in the oven at a temperature of 100 degrees 50-60 minutes. Cookies turns brittle and crispy!