RUB the butter with the icing sugar,salt and vanilla sugar.

Add the sifted flour and knead the dough.

Divide the dough in half. One half, knead well so the dough doesn't stick to hands. In the second half to add cocoa powder and knead well too. Flatten the dough balls, wrap in foil, put in refrigerator for 1-2 hours.

Both balls split in half. Roll each half into a rectangular formation. It is advisable to do this in a food tape for greater convenience, it will be easy to wrap.

One white and one black rectangle and put aside (we will wrap up our stripes). Cut 1 white and 1 black rectangles into strips approximately the same width as the height of the rectangle is rolled out to a breakdown they looked square shape.(Approximately 16 pages

About midway begin to lay out staggered test strips: the white rectangle, black stripe, white stripe, then black, again white, this layer lubricates the beaten egg yolk and so four layers upward; in the black rectangle, white stripe, black stripe, white again, then black, grease with beaten egg yolk and so, too, four layers up. Supporting rectangle on the bottom for the tape, with one hand, begin to wrap it. So done with two layers: rectangles, wrap around the stripes.

These briquettes are sent in the fridge for 1 hour.

Preheat the oven to 180 degrees. Take the briquettes out of the fridge and cut into even slices and spread on a not greased cookie sheet.

Bake in preheated oven for 12-15 minutes. Cookies should not brown much, and to stay bright to better emphasize the effect of dark-light test. And now try. Bon Appetit!!!