Preheat oven to 350° F.
Line a 9 inch cake pan with grease proof or other non-stick paper and grease the pan.
Break the chocolate into small pieces and melt it with butter over hot water.
Beat the egg yolks with half of the sugar.
Fold in the melted butter and chocolate mixture.
Beat egg whites until frothy; gradually add the remaining sugar, beating until stiff peaks form.
Fold in the beaten egg whites.
Bake at 350° for 40 minutes or until a wooden pick inserted in center comes out clean.
Use a knife to separate the cake from the non-stick paper. Please observe that the cake is quite sticky!
The Flourless Chocolate Cake can be served warm or cold with whipped cream.
The cream can be dusted with cocoa powder before serving, and the cake may be
dusted with powdered sugar.