Whip the cream until stiff. Beat the eggs, sugar and vanilla sugar with the whisk of the mixer until white and creamy. Fold in the cream. Warm up the nougat cream and let it cool down a bit. Chop the chocolate.
Line a crate mould (1.5 l capacity) with cling film. Pour ice cream into the mould or into 1 empty, clean plastic ice pack (approx. 1.5 l capacity). Pour the liquid nougat cream and the chopped chocolate onto the cream.
Stir with a fork 1-2 times so that the mixture is swirled. Cover the ice cream with foil and freeze for at least 8 hours (preferably overnight).
10-15 minutes before serving, remove the semifreddo from the mould, remove the foil and let it thaw. Dust Semifreddo with cocoa and cut it off in portions, refreeze the rest.