Combine 1 1/3 cups whipping cream, 1/3 cup butter and 3 tablespoons sugar in saucepan. Cook over medium heat, stirring constantly, until butter is melted and mixture comes to a boil. Remove from heat; add 16 ounces bittersweet chocolate and 2 teaspoons vanilla, let stand 1 minute. Stir until chocolate is melted and mixture is smooth. Let stand at room temperature 1 1/2-2 hours or until mixture is thick enough to spread.
Heat oven to 350°F. Butter 2 (9-inch) round cake pans. Line bottom of each pan with parchment or waxed paper, cut to fit.
Combine flour, cocoa, baking soda and salt in bowl; set aside.
Combine 1 3/4 cups sugar and 1/2 cup butter in bowl; beat at medium speed until well mixed. Add 1 egg at a time, beating well after each addition. Add 3 ounces melted chocolate and 2 teaspoons vanilla; beat until well mixed. Add flour mixture alternately with buttermilk, beating at low speed after each addition until well mixed.
Divide batter evenly between prepared pans. Bake 28-32 minutes or until toothpick inserted into center comes out clean. Cool in pans 10 minutes. Invert cakes onto cooling rack; remove parchment paper. Cool completely.
Combine all filling ingredients except raspberries in bowl; beat at high speed until stiff peaks form. Place 1 1/2 cups whipped cream mixture in bowl; refrigerate. Gently stir raspberries into remaining whipped cream mixture.
Cut each cake layer in half horizontally using long serrated knife. Place 1 layer, cut-side up onto cake plate. Spread 1/3 cup chocolate glaze over cake. Spread 1 1/2 cups raspberry filling over glaze. Place second cake layer on top, cut-side down. Repeat layering with remaining glaze, filling and cake layers.
Spread thin layer of glaze around sides and on top of cake. Refrigerate 10 minutes. Spread remaining glaze around sides of cake. Spread or pipe reserved whipped cream mixture over top of cake. Decorate with raspberries, if desired. Refrigerate cake at least 1 hour or up to 8 hours before serving.
Remove cake from refrigerator 15 minutes before serving. Store refrigerated.
*Substitute 4 teaspoons vinegar or lemon juice and enough milk to equal 1 1/4 cups; let stand 5 minutes.