Double-chocolate Tangerine Mousse Cake

-MOUSSE-
3 c Strained fresh tangerine or
-orange juice
1/3 c Sugar
2 1/2 ts Unflavored gelatin
3 tb Fresh lemon juice
14 oz Imported white chocolate;
-(such as Callebaut
; or Lindt), chopped
6 tb Sour cream
2 c Chilled whipping cream
9 oz Imported white chocolate;
-(such as Callebaut
; or Lindt)
Unsweetened cocoa powder
Fresh raspberries
Fresh mint sprigs

For Cake:

Preheat oven to 325F. Butter 9-inch-diameter springform pan with 2
1/2-inch-high sides. Line bottom with parchment. Butter parchment. Dust pan
with flour. Melt butter and chocolate in heavy large saucepan over low
heat, stirring constantly until smooth and melted. Remove from heat and
whisk in sugar, eggs and ground nuts. Pour batter into prepared pan. Bake
cake until toothpick inserted into center comes out with very moist crumbs
attached, about 45 minutes. Cool completely on rack (cake will fall and
crack).

Release cake pan sides. Turn out cake onto work surface. Peel off
parchment. Cut off outer 1/2-inch edge of cake. Clean cake pan. Reattach
cake pan sides; brush sides of pan with vegetable oil. Set cake in center
of pan (there will be space around cake that will be filled in with
mousse). Refrigerate cake.

For Mousse:

Boil tangerine juice and sugar in heavy large saucepan until reduced to 1
1/2 cups, about 20 minutes.

Meanwhile, sprinkle gelatin over lemon juice in small bowl. Let stand 10
minutes to soften.

Add gelatin mixture to tangerine juice mixture and stir to dissolve. Add 14
ounces white chocolate and whisk over low heat just until melted. Whisk in
sour cream. Pour into large bowl. Chill mixture until cool and thickened
but not set, whisking occasionally, about 1 hour 45 minutes.

Beat chilled whipping cream to stiff peaks. Fold into white chocolate
mixture. Pour mousse over cake in pan, covering top and sides completely.
Refrigerate cake overnight.

Using vegetable peeler, shave 9 ounces white chocolate into thin curls (if
white chocolate is too hard to shave, place briefly in warm place to soften
slightly). Run small sharp knife around pan sides to loosen cake. Release
pan sides. Place cake on platter. Sprinkle chocolate curls over top of
cake. Press more chocolate curls around sides of cake, covering completely.
Place cocoa powder in fine sieve. Dust cocoa very lightly over chocolate
curls. (Can be prepared 1 day ahead. Cover and refrigerate.) Garnish cake
with raspberries and mint sprigs. Serve cold.

Serves 12.