Chocolate fudge cake (a. k. a. death by chocolate)

MMMMM----- Recipe via Meal-Master (tm) v8.01
  
       Title: Chocolate Fudge Cake (A. K. A. Death By Chocolate)
  Categories: Chocolate, Cakes
       Yield: 6 servings
  
      10 oz Baker's semi-sweet chocolate
            -(do not substitute)
     1/2 c  Lightly salted butter
       6 lg Eggs, separated, at room
            -temperature
       1 c  Granulated sugar
       2    To 4 tsp creme de cacao,
            -Kahlua or dark rum
     1/2 ts Vanilla
            Butter and powdered cocoa
            -for the pan
            Frosting:
       1 c  Sour cream at room
            -temperature
      14 oz Baker's semi-sweet chocolate
            -(do not substitute)
  
   Cake:
   
   Place oven rack in lower third of the oven, and preheat oven to 375
   degrees.  Butter an 8 inch springform pan, and coat with powdered
   cocoa.
   
   Melt chocolate and butter in a double boiler over hot, but *not
   boiling*, water. (don't rush this step, chocolate burns easily)
   
   Beat egg yolks in a lg mixer bowl at high speed, gradually adding 3/4
   c of the granulated sugar.  Beat until yolk mixture is pale yellow
   and thick, 4 to 6 minutes.  Add melted chocolate mixture to the yolk
   mixture. Beat until completely smooth.  Add vanilla and liquor of
   your choice. Beat until blended.
   
   Beat egg whites in mdm mixer bowl at high speed until soft peaks form.
   Gradually beat remaining 1/4 c granulated sugar into whites; continue
   beating until stiff but not dry peaks form. Fold whites *gently* but
   thoroughly into chocolate mixture.  Pour batter evenly into pan;
   smooth top.
   
   Bake 15 minutes.  Reduce oven to 350 degrees; bake another 15 minutes.
   Reduce oven temp to 250; bake 30 minutes longer (total baking time is
   1 hour).  Turn off oven; prop open oven door and allow cake to remain
   in oven for 30 minutes.  Remove cake from oven and cover top with
   damp paper towelling; let stand 5 minutes.
   
   Remove towelling and cool cake completely.  Dome of cake will crack
   and collapse; this is normal - press top of cake down lightly to
   smooth top. Remove springform and transfer cake to serving platter.
   
   To make the frosting:
   
   Melt chocolate in double boiler over hot but not boiling water. Using
   a wooden spoon, mix in sour cream.  Pour over the cake. Let cool and
   harden.
  
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