Preheat oven to 375°F. Mix butter and flour with a pastry blender until the mixture forms crumbs.
Mix in 4tablespoons sugar, the salt, lemon rind, egg yolks and sour cream; knead till the mixture becomes a homogeneous dough. Cover it with a cloth and let it rest in the refrigerator.
Cut three quarters of the dough into 12 even pieces. With these line 2½-inch fluted round cupcake or basket molds with a thin layer of dough.
Cut remaining quarter of dough into 12pieces. Stretch each piece with a rolling pin to get 6-inch pieces. Roll each piece separately and twist into a thin crescent. Make sure that the curve of the crescents is as wide as the widest part of the molds so they will fit.
Place the filled molds and the crescents on separate pastry sheets and bake them in the preheated oven for 12 to 15 minutes, or until they are well baked and colored.
Whip heavy cream with remaining 3tablespoons vanilla sugar; gently mix it with currant jam.
Fill each basket with some of the cream mixture, and place a twisted crescent as the handle of the basket. The whipped cream will hold it in place.
Other fillings could be fresh raspberries or wild strawberries or freshly grated chocolate mixed with whipped cream.