Grease a 9x13 inch glass pan or 10-11 inch springform pan and preheat the oven to 325°F.
For the base, beat butter and sugar, then add the egg and sour cream. Mix in the flour, baking powder, and salt to form a soft dough. Chill for half an hour, then roll out and place in the prepared pan.
For the second layer, finely cut up the dry cottage cheese and mix with egg yolks, vanilla sauce, whipping cream, ½ cup sugar, and salt. Beat egg whites with the remaining ½ cup sugar until stiff, then fold into the cottage cheese mixture. Spread onto the base.
Bake at 325°F for 1 hour, plus an additional 5 minutes if needed. Allow to cool, then refrigerate before serving with icing sugar or fruit topping.
