1. Preheat oven to 325 degrees F. Have ready an ungreased 10-inch tube pan, preferably with a removable bottom. Line the bottom with waxed or parchment paper, cut to fit.
2. Sift flour and 3/4 cup of the sugar together into a medium bowl. Whisk to mix thoroughly, and set aside.
3. Place egg whites in a very large bowl. Using an electric mixer on medium speed, beat until foamy. Beat in cream of tartar, salt, and vanilla. Increase speed to high. Gradually beat in remaining 3/4 cup sugar, 1 Tbsp. at a time, and beat until stiff, satiny peaks form, about 7 to 9 minutes. If using a handheld mixer, move beaters around the bowl to help volume increase.
4. Sprinkle flour mixture, 1/4 cup at a time, over top of egg whites and fold into meringue just until incorporated. Fold in chocolate.
5. Transfer batter to the tube pan. Smooth top gently. Bake until golden brown and a tester inserted in the cake comes out clean, about 45 to 50 minutes.
6. Invert pan on its feet or on the neck of a bottle or funnel to cool completely, about 11/2 to 2 hours.
7. Run a knife around tube and edge of pan to loosen cake. Invert cake onto a plate and peel off waxed paper. Sift confectioners' sugar over the top. To serve, slice with a serrated knife using a gentle sawing motion. If desired, top with additional chopped chocolate, berries, and mint sprigs.
Source: Hannaford fresh Magazine, March - April 2015