1 cup chopped walnuts
2 tablespoons plus 1/2 cup sugar, divided
9 oz. 70% bittersweet chocolate, coarsely chopped
1 tablespoon grated orange peel
1/8 teaspoon salt
7 egg whites
1/4 teaspoon cream of tartar
1 cup heavy whipping cream
2 to 3 teaspoons sugar
1/2 teaspoon vanilla extract
1. Heat oven to 350°F. Lightly spray sides of 9-inch springform pan with cooking spray; line bottom with parchment paper.
2. Pulse walnuts and 1 tablespoon of the sugar in food processor until very finely ground, being careful walnuts don't become a paste; place in medium bowl. Wipe excess oil from food processor. Pulse chocolate and 1 tablespoon of the sugar until mixture resembles crumbs ranging from very finely chopped to 1/4-inch pieces. Add to nuts, along with orange peel and salt; stir to combine.
3. Beat egg whites and cream of tartar in large bowl at medium speed until soft peaks form. Gradually add remaining 1/2 cup sugar, beating until egg whites are stiff and glossy but not dry, 2 to 3 minutes. Gently scrape into large wide bowl.
4. Pour half of the chocolate mixture over egg whites; fold in until nearly incorporated. Repeat with remaining chocolate mixture, folding just until incorporated. Place in springform pan; spread gently to level.
5. Bake 30 to 35 minutes or until torte is puffed and golden brown on top and springs back when pressed gently with fingers. (A toothpick inserted in center will emerge moist and stained with a little melted chocolate, but not coated with batter.) Cake may crack slightly. Cool on wire rack 10 minutes. Slide thin knife or spatula around sides of pan; cool completely. Serve at room temperature. (Cake can be made 1 day ahead. Cover and store at room temperature.)
6. Meanwhile, beat all cream ingredients in medium bowl at medium-high speed until soft peaks form. Serve with cake. Store whipping cream in refrigerator.
PER SERVING: 445 calories, 33 g total fat (15 g saturated fat), 8 g protein, 37.5 g carbohydrate, 40 mg cholesterol, 100 mg sodium, 3.5 g fiber