Dark Chocolate Semifreddo

Directions

1. 1
   Combine chocolate, vanilla, and 1/4 tsp. salt in a medium heatproof bowl. Heat 1 1/2 cups cream in a small saucepan over medium until barely simmering. Pour hot cream over chocolate mixture and let sit until chocolate is melted, about 5 minutes. Whisk chocolate mixture until combined and smooth. Chill, stirring occasionally, until cold, about 1 hour.
2. 2
   Beat egg whites and a pinch of salt on high speed in the bowl of a stand mixer fitted with whisk attachment until soft peaks form.
3. 3
   Meanwhile, cook sugar and 1/3 cup water in a small saucepan over medium-low heat, stirring, until sugar is dissolved. Clip thermometer to the side of saucepan; increase heat to medium. Bring to a boil without stirring and cook until thermometer registers 250°F.
4. 4
   Working quickly and with motor running, pour syrup into egg whites in a steady stream, avoiding whisk so syrup doesn't splatter. Beat until glossy, stiff peaks form (be careful not to overbeat).
5. 5
   Using an electric mixer, beat chilled chocolate mixture until soft peaks form. Gently fold in meringue, leaving a few streaks. Scrape into a large loaf pan and cover. Freeze until solid, at least 3 hours and up to 3 days.
6. 6
   Just before serving, let semifreddo sit at room temperature 15 minutes. Beat remaining 1 cup cream in a small bowl until soft peaks form. Serve scoops of semifreddo in small bowls with whipped cream.