Prepare the shortcrust pastry and refrigerate for at least 1 hour.
Roll out about half of the dough and line the tart pan or a springform pan (28 or 30 cm) with it.
Boil the currants with sugar and starch thickly over low heat and allow to cool.
Beat the egg with sugar until creamy, stir with the quark and sour cream until smooth and spread on the pastry base. Spread the currant mixture on top.
Roll out the remaining dough and place a grid over the mass. Press the edges well. Shape the rest of the dough into rolls and use them to fold the edge.