METHOD

1. Lightly grease and line a 22cm x 8cm loaf tin with non-stick baking paper. Dust the sides and base of the tin with the crushed chocolate biscuits. Set aside.
2. Place the chocolate and cocoa in a heatproof bowl over a saucepan of simmering water and stir until smooth. Set aside.
3. Place the eggs, extra yolks, vanilla and sugar in a heatproof bowl over a saucepan of simmering water and, using a hand-held electric mixer, beat for 6–8 minutes or until thick and pale. Remove from heat and beat for a further 6–8 minutes or until cool. Gently fold through the melted chocolate mixture and set aside. 
4. Whisk the cream until soft peaks form.Gently fold cream through the egg mixture until well combined and pour into the prepared tin. Cover with foil and freeze for 4–6 hours or until firm.
5. To make the caramel, place the cream, butter and sugar in a saucepan over low heat and stir until the sugar is dissolved. Increase the heat to medium, bring to the boil, and cook for 5–7 minutes or until thickened. Allow to cool. 
6. Slice the semifreddo, drizzle over the caramel sauce and sprinkle with the sea salt to serve. Serves 6–8.