3 c. semi-sweet chocolate chips (about 1 1/4 lb.)
1 c. whipping cream
4 extra lg. egg yolks
1 c. chilled whipping cream
8 extra lg. egg whites, room temperature

SAUCE:

1 1/4 c. sugar
1/4 c. water
1 c. whipping cream
1/2 c. (1 stick) unsalted butter, cut into pieces
1 tsp. vanilla extract

For Mousse: Melt chocolate chips in heavy medium saucepan over very low heat, stirring until smooth. Add 1 cup cream and stir until smooth. Pour into large bowl. Cool to room temperature. Whisk yolks into chocolate mixture. Using electric mixer, whip 1 cup chilled cream in medium bowl until soft peaks form. Using electric mixer fitted with clean dry beaters, beat whites in another large bowl until soft but not dry. Fold whipped cream into chocolate mixture. Gently fold in whites. Pour mixture into 10 inch diameter springform pan with 2 inches high sides. Cover and freeze at least 6 hours or overnight. (Can be prepared up to 2 days in advance.)

For Sauce: Cook sugar and water in heavy medium saucepan over low heat, stirring until sugar dissolves. Increase heat and boil without stirring until syrup turns caramel color. Add cream (mixture will bubble vigorously) and stir until smooth. (Can be prepared 1 day ahead. Cover and refrigerate. Rewarm over low heat before using, stirring frequently.)

Place mousse in refrigerator for 30 minutes to soften slightly. Run small sharp knife around cake pan sides to loosen. Release pan sides. Cut mousse into wedges. Ladle warm caramel sauce onto plates. Place mousse wedges atop sauce. Sprinkle additional chocolate chips over sauce.