Mix the flour, cornstarch, cocoa and baking powder for the dough. Add sugar, vanilla sugar, salt, eggs and butter and work into a smooth dough. Stir in the chocolate grater. Place a baking frame (approx. 30 x 40 cm) on a baking sheet and spread the dough on the sheet.
Drain the pears and collect the juice, you will need it later. Cut the pears into fine wedges and spread them on the dough.
Bake for about 25 minutes at 180 ° C (hot air at 160 ° C).
Let the base cool on the baking sheet.
Whip the cream a little for the topping. Mix the powdered sugar, vanilla sugar and cream stiffener, add and whip the cream until completely stiff. Mix the sour cream with pear juice, fold in the cream and spread on the base.
Remove the baking frame.
To decorate, mix powdered sugar and cocoa and sieve over it, decorate with chocolate decorative leaves or ornaments. Cut the cake into approx. 24 pieces and serve.