Preheat oven to 350 degrees.
In an extra-large bowl let egg whites stand at room temperatures for 30 minutes.
Meanwhile, sift the 1 1/2 cups powdered sugar, the flour, and cocoa powder together 3 times; set aside.
Add cream of tartar and vanilla to egg whites.
Beat with an electric mixer on medium speed until soft peaks form.
Gradually add granulated sugar, 2 tablespoons at a time, beating on high speed until stiff peaks form.
Sift about one-fourth of the flour mixture over beaten eggs whites; fold in gently.
Repeat, folding in remaining flour mixture by fourths. Pour into an ungreased 10-inch tube pan.
Using a knife, gently cut through batter to remove any large air pockets.
Bake on the lowest rack in oven for 40 to 45 minutes or until the top springs back when lightly touched.
Immediately invert the cake (leave pan); cool thoroughly.
Loosen side of cake from pan; remove pan.
For frosting, in a chilled medium bowl beat whipping cream with chilled beaters of an electric mixture on medium speed until soft peaks form.
Add the powdered sugar; beat just until combined.
Split cooled cake into 2 layers.
Place a layer, cut side up, on a serving plate.
Spread with some of the frosting.
Place secnd layer, cut side down, on top of the frosted layer.
Frost top and side with remaining frosting.
If desired, garnish with chocolate curls and fresh raspberries.