Crumble the torrone, put it in a saucepan with 75 ml of the cream and melt it over low heat. Pass it through a sieve to separate the nuts and let the liquid cool, then chop the sieved nuts into small pieces.
Whip the remaining cream with the vanilla sugar until stiff. Beat the egg yolks with the sugar until pale and creamy, then fold in half of the whipped cream and the torrone-infused cream. Fold in two-thirds of the pistachios, the chopped nuts from the sieve and the remaining whipped cream.
Line a small loaf tin (about 20 x 11 cm | 8-inches x 4-inches) with plastic wrap. Soak the sponge fingers with Spumante. Pour in the torrone mixture to a height of about 2 cm and cover with a layer of ladyfingers. Fill in another thick layer of torrone mixture and cover it with the remaining ladyfingers. Fill everything up with the remaining torrone mixture, smooth it out and cover it with foil. Let everything freeze for about 4 hours.
Turn the semifreddo out of the mold onto a plate and remove the foil. Sprinkle with the remaining pistachios, top diagonally with Torrone slices and serve. Serve with a chocolate sauce, if desired.