100 % cocoa chocolate is difficult to find. Choose a bitter chocolate with at least 70 % cocoa content. Break the chocolate into pieces over a double boiler. Add 5 1/2 oz of butter (cut into pieces) and the caster sugar. Warm over a moderate heat and gently let the ingredients melt. Take off the heat and blend until smooth. Separate the eggs. Add the yolks, one at a time, into the batter, then sift and sprinkle with the flour. Whisk the egg whites stiff and gently fold them into the mixture. Pour into a buttered cake pan. Bake for 40 to 45 minutes at 300 F. Watch closely, the cake has to remain moist and tender to the touch. Let it cool completly before unmolding it on a serving dish. Serve it with a custard cream flavored with orange-flower water (2 teaspoon for 1 quart of milk, 5 oz of sugar, 1 vanilla pod and 12 egg yolks).
