Solothurner nusstorte (solothurn hazelnuts gateau)

------------------------------BASE AND TOPPING------------------------------
      3    Egg whites
    100 g  Sugar
    100 g  Hazelnuts, ground
     20 g  Cornflour

--------------------------------butter CREAM--------------------------------
    150 g  Unsalted butter
    120 g  Icing sugar
     50 g  Hazelnuts, roasted and
           -- coarsely ground

-----------------------------------SPONGE-----------------------------------
    150 g  butter
    150 g  Sugar
      3    Eggs, separated
    100 g  flour
     20 g  Cornflour
     50 g  Hazelnuts, roasted and
           -- ground
 
  FOR A 22 CM DIAMETER TIN BASE TOPPING: Beat the egg whites and sugar to a
  stiff meringue (adding sugar gradually) and fold in the hazelnuts and
  cornflour. Mark 2 circles, 22 cm diameter, on a greased and floured baking
  tray. Using a plain nozzle, pipe the mixture onto the tray, covering the
  two circles to a depth of 1/2 cm. Bake for 12 to 15 minutes at 160 oC, then
  remove from the baking tray WHILST HOT. Allow to cool. When cold, spread a
  thin layer of butter cream on one circle, cover with the sponge (recipe
  below) and then spread a layer of butter cream over the sponge. Place the
  second circle on top, mask the sides with butter cream and coat these with
  the coarsely ground hazelnuts (roasted). Dust the finished gateau with
  icing sugar. SPONGE: Cream the butter and sugar. Add the egg yolks one at a
  time and continue beating. Mix the flour, cornflour and hazelnuts together.
  Fold the dry ingredients and the stiffly beaten egg whites into the creamed
  mixture alternately. Pour into a greased sponge tin (22 cm diameter) and
  bake for 20 minutes at 160-170 oC.