Assembly: Finely grind chopped chocolate in processor (do not overprocess or chocolate will clump together). Using serrated knife, cut each cake horizontally into 3 equal layers. Spread dab of frosting on 6-inch cardboard round; top with bottom layer of 6-inch cake, cut side up. Brush cake with 2 tablespoons syrup. Spread 1/2 cup frosting over. Sprinkle with 2 tablespoons ground chocolate. Top with middle 6-inch cake layer. Brush with 2 tablespoons syrup. Spread 1/2 cup frosting over. Sprinkle with 2 tablespoons ground chocolate. Brush 2 tablespoons syrup over cut side of top 6-inch cake layer. Using hands, turn cake layer over and place cut side down atop frosted layers. Cover and refrigerate cake. Spread dab of frosting on 9-inch cardboard round; top with bottom layer of 9-inch cake, cut side up. Brush with 1/4 cup syrup. Spread 1 cup frosting over. Sprinkle with 1/4 cup ground chocolate. Top with middle 9-inch cake layer. Brush with 1/4 cup syrup. Spread 1 cup frosting over. Sprinkle with 1/4 cup ground chocolate. Brush 1/4 cup syrup over cut side of top 9-inch cake layer. Slide large tart pan bottom or springform cake pan bottom under cake layer. Using pan bottom as aid, lift cake layer and turn cut side down atop frosted layers. Cover and refrigerate cake. Spread dab of frosting on 12-inch cardboard round; top with bottom layer of 12-inch cake, cut side up. Brush with 1/2 cup syrup. Spread 2 cups frosting over. Sprinkle with 1/2 cup ground chocolate. Top with middle 12-inch cake layer. Brush with 1/2 cup syrup. Spread 2 cups frosting over. Sprinkle with 1/2 cup ground chocolate. Brush 1/2 cup syrup over cut side of top 12-inch cake layer. Slide large tart pan bottom or cake pan bottom under cake. Using pan bottom as aid, lift cake layer and turn cut side down atop frosted layers. Cover cake; refrigerate all cakes until firm, about 4 hours. Cover remaining frosting and let stand at room temperature. Place 12-inch cake on its cardboard on large flat platter. Place platter on cake stand. Using icing spatula, spread 4 cups frosting over top and sides of cake; smooth top. Swirl frosting decoratively on sides of cake. Press 1 dowel into center of 12-inch cake. Mark dowel 1/4 inch above top of cake. Remove dowel and cut with serrated knife at marked point. Cut 4 more dowels to same length. Press 4 cut dowels into 12-inch cake, inserting 4 inches inward from cake edges and spacing evenly; press 1 dowel into center of cake. Refrigerate cake on platter. Place 9-inch cake on its cardboard on large flat plate or tart pan bottom. Place plate on cake stand. Using icing spatula, spread 3 cups frosting over top and sides of cake; smooth top. Swirl frosting decoratively on sides of cake. Press 1 dowel into center of 9-inch cake. Mark dowel 1/4 inch above top of cake. Remove dowel and cut at marked point. Cut remaining 3 dowels to same length. Press 4 cut dowels into 9-inch cake, inserting 3 inches inward from cake edges and spacing evenly. Refrigerate 9-inch cake on plate. Place 6-inch cake on its cardboard on another large flat plate or tart pan bottom. Place plate on cake stand. Using icing spatula, spread 2 cups frosting over top and sides of cake; smooth top. Swirl frosting decoratively on sides of cake. Refrigerate all cakes until frosting sets, about 2 hours. (Can be made 1 day ahead. Cover cakes and remaining frosting separately with plastic wrap; chill. Bring frosting to room temperature before continuing.) Using metal spatula as aid, gently place 9-inch cake on its cardboard atop 12-inch cake, centering carefully on dowels. Gently place 6-inch cake on its cardboard atop dowels in 9-inch cake. Spoon remaining frosting into pastry bag fitted with medium star tip. Pipe decorative border around base of 12-inch cake and around top edge of each tier. Arrange berries decoratively inside piped borders atop each tier. (Can be prepared 8 hours ahead; refrigerate.) Let cake stand at room temperature at least 3 and up to 6 hours before serving. Garnish with mint. Serving: Toss berries with sugar in large bowl. Let stand at least 30 minutes and up to 2 hours at room temperature. Remove top and middle cake tiers. Remove dowels from middle cake. Cut top and middle cakes into slices; transfer to plates. remove dowels from bottom cake. Starting 3 inches inward from edge of bottom cake and cutting through from top to bottom, cut 6-inch-diameter circle in center of cake. Cut outer portion of cake into slices, then cut inner portion into slices. Spoon berries around cake slices. Serves 50. Bon Appetit June 1995