Source: Julia Child - The French Chef cookbook

Cake
4 ounces (112 gr). semisweet chocolate
2 tablespoons (30 ml) dark rum
1/2 cup (125 ml) butter, unsalted, softened
2/3 cup (150 ml) granulated sugar
1/4 teaspoon (1 ml) cream of tartar
1 pinch salt
2 tablespoons (30 ml) granulated sugar
1/3 cup (80 ml) almonds, blanched, pulverized
1/4 teaspoon (1 ml) almond extract
3/4 cup (175 ml) flour, plain, bleached,
    sifted, less 1 1/2 tablespoons
3 eggs, separated

Frosting
3 (1 ounce  - 28 gr) squares semisweet chocolate
1 1/2 tablespoons (20 ml) dark rum or strong coffee
6 tablespoons (90 ml) butter, unsalted, softened

Cake: Grease with butter and flour an 8-inch cake pan. Melt the chocolate in a bowl in the microwave and mix it with the rum. Set aside. Measure the remaining ingredients before continuing. Cream the butter and sugar together until soft and fluffy, then beat in the egg yolks.

Preheat the oven to 350 degrees F (175 degrees C) and make sure the oven rack is in the center of the oven.

Clean the beaters of all fat and in a separate bowl whip the egg whites on low speed until they begin to foam. Add the cream of tartar and salt, and gradually increase beating speed to fast. When the egg whites hold their shape in a soft mass, beat in the 1/4 cup (60 ml) of sugar and continue beating until you can lift a bit of the mixture in a rubber spatula and they hold their shape, dropping off into a little point with a curling tip. The texture should be smooth and shiny, not dry. Set the egg whites aside.

Stir up the chocolate to make a perfectly smooth soft cream. Stir the chocolate into the butter, sugar and yolk mixture. Add the almonds, almond extract and flour. With a rubber spatula, stir in one fourth of the beaten egg whites to soften the batter, then scoop the rest on top of the batter. Rapidly and delicately fold in the egg whites, revolving the bowl as you go, until egg whites and batter are blended. This should take not more than one minute. Turn the batter into the prepared pan, tilting pan in all directions so cake will bake evenly and not be larger in the center. Bake for 25 minutes. Cake is done when it has puffed to top of pan. Put foil over the top of the cake if it starts to get too brown. When cake is done, the center will still move slightly when pan is shaken. A wooden pick plunged into the 2 1/2 to 3 inch outermost circumference of the cake (i.e. not in the center) should come out clean. If the cake is not quite done, bake a few minutes more. Allow to cool in the pan for 10 minutes, then run a knife around the edge of the pan, invert a cake rack over the top of the pan and turn the pan upside down to unmold the cake onto the rack. Allow cake to cool for 2 hours before icing.

Frosting: Melt the chocolate in the microwave and mix in the rum. Beat in the butter one tbsp at a time, beating until perfectly smooth. Then beat over cold water, if necessary, until icing is of spreading consistency. Ice the cake and decorate with slivered almonds, if desired.