Put Russian bread in a freezer bag, close the bag and finely crush the pastry with the rolling pin.
Mix flour with baking powder. Add the breadcrumbs, sugar and vanilla sugar. Mix well. Add eggs, oil and milk and stir well. Put the batter in a springform pan and put it in the oven.
Bake at top / bottom heat 200 ° (preheated), hot air 180 °, gas level 3 for 25-30 minutes.
Mix the sour cream with condensed milk and spread on the warm cake. Let the cake cool down.