3/4 cup superfine sugar, plus some for sprinkling
10 ounces semisweet chocolate, chopped
3/4 cup unsalted butter, cut into pieces
2 teaspoons vanilla extract
5 eggs, separated
1/4 cup flour, sifted
pinch of salt
powdered sugar, for dusting
Heat oven to 325. Generously butter a 9 1/2 inch springfgorm pan, then sprinkle the pan with a little sugar and tap out the excess.
Set aside 3 tablespoons of the sugar. Place the chocolate, butter, and remaining sugar in a heavy saucepan and cook over low heat until the chocolate and butter have melted and the sugar has dissolved. Remove the pan from the heat, stir in vanilla, and let mixture cool slightly.
Beat egg yolks into the chocolate mixture, beating each well, then stir in flour.
In a clean, greasefree bowl, beat egg whiltes slowly until they are frothy. Increase the speed, add salt, and continue beating until soft peaks form. Sprinkle over the reserved sugar and beat until the whites are stiff and glossy. Beat one-third of the whites into the chocolate mixture, then fold in the remaining whites.
Carefully pour the mixture into the pan and tap the pan gently to relase any air bubbles.
Bake for about 35-45 minutes, until well-risen and the top springs back when touch lightly with a fingertip. Transfer to a wire rack. remove the side of the pan, and let cool completly.
Remove the pan base and dust cake with powdered sugar before serving.
from: French (Clements and Cohen).