Method
1 Preheat oven to 325°F. Grease the sides and bottom of a 10-inch springform pan. Add a few tablespoons of sugar and gently shake so that all the sides and bottom of the pan are coated with sugar. Tap out excess sugar.
2 Beat egg yolks with the granulated sugar until they are thick and pale yellow and form a ribbon when they fall from the beater.
3 Place chocolate and 3 Tbsp of water in the top of a double boiler. Melt over simmering water, whisking until smooth. If the chocolate gets too thick, and looks like it will firm up, whisk in a tablespoon or more of water. Let cool slightly.
4 Fold the warm chocolate into the egg mixture. Stir in the softened butter. Stir in the grated orange peel. Fold in the sifted flour. Mix thoroughly but gently.
5 Beat egg whites until stiff. Stir a large spoonful of the chocolate mixture into the beaten egg whites. Mix well. Pour this mixture into the chocolate mixture, fold together gently, incorporating the whites completely. Be careful at this stage not to overmix.
6 Turn batter into the springform pan. It will come close to the top of the pan. Set the pan on the middle rack of your oven and bake for 1 hour and 20 minutes, or until a cake tester inserted in the center comes out clean. Cool on a rack for 15 minutes, then remove the outer rim. Allow the cake to cool completely before removing the bottom of the pan. Refrigerate.
7 When ready to serve, sprinkle with powdered sugar.
Makes 20 small, but quite rich, servings.
