Instructions

1. Place chopped chocolate in a large bowl.
2. Heat 1 cup cream in a small saucepan over medium-low heat until bubbles begin to form around edges of pan. Remove from heat, and immediately pour cream over chocolate; let stand 1 minute. Stir until chocolate is melted and mixture is smooth.
3. Chill at least 4 hours or until mixture is very cold.
4. Whisk together egg whites and granulated sugar in top of a double boiler set over simmering water. Cook egg mixture, stirring occasionally, until a candy thermometer reads 140°F.
5. Immediately transfer egg mixture to a heavy-duty stand mixer. Beat at high speed 10 minutes or until mixture is thick, white, and glossy. Stir in orange zest.
6. Meanwhile, beat chocolate mixture at medium speed with mixer until soft peaks form. Stir chocolate mixture into egg white mixture until blended. Spoon into a 9- x 5-inch loaf pan lined with plastic wrap. Wrap tightly with plastic wrap. Gently tap bottom of pan onto counter to release any air bubbles. Freeze at least 8 hours or up to 1 week.
7. Beat 2 cups cream at medium-high speed with mixer until slightly thickened. Gradually add powdered sugar, beating until soft peaks form.
8. Unmold semifreddo, and cut into 1-inch-thick slices. Serve with whipped cream, orange sections, and chopped nuts.