Mix the softened butter with the sugar and vanilla sugar until frothy. Add the eggs one after the other and stir in each egg for about 1/2 minute until the mixture has become thick and foamy. Slowly pour in the egg liqueur while stirring.
Mix the flour with the cornstarch and baking powder and sift into the egg-butter mixture. Stir in briefly. Then fold in the white chocolate and macadamia nuts.
Put in a greased and floured Gugelhupf tin (diameter 22 cm) and bake at 180 ° for about 50 minutes. Make a chopstick test.
When the cake is cold, you can decorate it either with powdered sugar or with chocolate icing.