Hazelnut Custard Cake with Currants
For the cake, cream together butter and sugar. Knead in flour, hazelnuts and the egg into a smooth, firm dough. Shape into a disc, cover with plastic wrap and refrigerate for 30 minutes.
Then roll out the dough to 1/2 cm (approximately 1/8 inch) thick and press into a greased springform pan.
For the topping, separate the eggs. Stir together the kefir with sugar and egg yolks. Stir in the cornstarch. Beat the egg whites until stiff and fold into the kefir mixture. Fill the cake pan. Bake in an oven preheated to 180°C (approximately 350°F). Bake about 45 minutes until golden. Remove and let cool.
For the garnish, dust the currants with powdered sugar. Top the cake with the currants. Serve sliced.