Butter
8 egg yolks
1 c. sugar
7 oz. bittersweet chocolate, melted and cooled
1 tsp. vanilla
2 c. walnuts, finely ground
8 egg whites
Cream of tartar
Salt
8 oz. semi-sweet chocolate
Walnut halves for decoration (optional)

Preheat oven to 350 degrees. Generously grease a 9 inch springform pan with butter. Set aside. In a large bowl, beat the egg yolks with the sugar for 5 minutes. Fold in melted chocolate, vanilla, and walnuts.

In another bowl, beat the egg whites with a pinch of cream of tartar and a pinch of salt until the whites hold soft peaks. Stir 1/4 of the egg whites into chocolate mixture. Fold in the remaining whites gently but thoroughly.

Pour into the pan and bake in a 350 degree oven for 45 minutes to 1 hour, or until a cake tester comes out clean. Allow the cake to cool in the pan for 15 minutes, then remove sides of the pan. Invert the cake onto a rack. Cool completely.

For the icing, melt the semi-sweet chocolate. Cool about 5 minutes, then spread over tops and sides of cooled cake. Decorate with walnut halves if desired.