Heat oven to 350 degrees. Grease and flour 2 round pans, 9 x 1 1/2 inches. Prepare 1 package frosted brownie mix as directed except divide batter evenly between pans. Bake 20 minutes. Cool 15 minutes; remove from pans. Cool completely on wire rack. Beat frosting and 1 cup whipping cream in large bowl on high speed, scraping bowl constantly, until stiff. Fill layers and frost top and side of torte with frosting mixture. Garnish with grated chocolate if desired. Refrigerate any remaining torte.