Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
   1      pound         bittersweet chocolate
     1/4  cup           sugar
     1/2  pound         butter -- cut in small pieces
     1/4  cup           flour -- unbleached
  10                    eggs -- separated
   1      tablespoon    lemon juice

Preparation:

Preheat oven to 400. Butter a 9" springform pan or deep nonstick cake pan. Break the chocolate into pieces, melt in top of a double boiler placed over boiling water, stirring from time to time. Off the heat, stir the butter into the chocolate, stirring until the butter and chocolate are combined. Transfer to a large mixing bowl. In a copper bowl, beat whites with lemon juice over direct heat, whisking constantly until it reaches body temp. Transfer to a large bowl and beat the egg whites until they form soft peaks; add 1/2 the sugar and beat until firm peaks; do not overbeat. In a medium-size mixing bowl, whisk the egg yolks and the other half of the sugar until frothy and lemon-colored. Add the flour to the yolk mixture and mix thoroughly. Fold the egg yolk mixture into the chocolate mixture. Add of the egg whites to the chocolate batter and blend thoroughly. Very gently fold in the remaining whites. Do this slowly and patiently until no streaks of white remain. Pour the batter into the prepared pan. Bake for just 17 minutes. Remove from oven, cover the pan with a plate for an additional 12 minutes to keep the cake very moist and supple. Serve room temperature. Great served with vanilla ice cream and chocolate sauce!