Ingredients

  • 1 cup (2 sticks) unsalted butter
  • 9 ounces bittersweet (not unsweetened) or semisweet chocolate, chopped
  • 3/4 cup sugar
  • 5 large eggs
  • 1/2 cup ground toasted hazelnuts
  • 3 cups strained fresh tangerine or orange juice
  • 1/3 cup sugar
  • 2 1/2 teaspoons unflavored gelatin
  • 3 tablespoons fresh lemon juice
  • 14 ounces imported white chocolate (such as Callebaut or Lindt), chopped
  • 6 tablespoons sour cream
  • 2 cups chilled whipping cream
  • 9 ounces imported white chocolate (such as Callebaut or Lindt)
  • Unsweetened cocoa powder
  • Fresh raspberries
  • Fresh mint sprigs

Method

  • 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.
  • 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.