Mix the butter, sugar, vanilla sugar and rum until creamy. Beat in egg yolks one by one. Beat the egg whites until stiff.
Carefully fold in the ground nuts, sifted flour, baking powder, egg whites and cream alternately. Halve the Roche balls and carefully fold in with a spatula, not with the mixer, because then you destroy the pralines.
Fill into a greased, floured Guglhupf pan and bake at 175 degrees for about 60 minutes.
Let the cake cool down a bit and turn it out.
Decorate with chocolate icing and the remaining pralines.