This Esterhazy Torte a.k.a the Hungarian dream takes some time to put together, but I'll guarantee you will not regret it after your first bite. It's definitely what sweet dreams are made of.
Grind remaining hazelnuts into 2 batches of 2-1/2 cups (250 gm) and 1-1/2 cups (150 gm) for the sponge layers and the filling. Don't turn them into nut butter just grind finely.
Preheat the oven to325° F. Don't use convection (fan). With an electric mixer beat egg whites while gradually add the sugar and vanilla sugar for about 5 minutes until stiff peaks form.