Sift the flour onto the surface, make a dent in the center. Dice the cold butter and fill it into the indentation. With fingertips, rub flour and butter together until crumbly, add sugar and salt.
Repeatedly press a bulge in the center, pour in egg yolks, vanilla sugar and orange zest, and quickly work the whole thing into a smooth dough.
Form into a plastic bag and rest in the refrigerator for about 1 hour.