From, Ultimate Cake, by Barbara Maher

Ingredients:
5 1/2 oz (160g) Callebaut Semisweet Pastilles
2 Tbs unsalted butter
1 egg yolk
1/4 cup (60g) granulated sugar
4 egg whites

Grease an 8-inch spring form pan and line the bottom of the pan with parchment paper.  This can be done by using a piece of parchment a little larger than the bottom of the pan.  Remove the side from the pan, place the parchment on the bottom of the pan and then replace the sides of the pan.  Some parchment will stick out the sides of the pan.  If there is a large amount of paper sticking out the sides just trim it.  Preheat oven to 350° F.

Melt chocolate and butter together in a double boiler; allow to cool.  In a separate bowl, whisk the egg yolk and 1 Tbs sugar together until pale and fluffy.  Stir in melted chocolate. 

In another bowl, using a balloon whisk or an electric mixer, whisk the egg whites into soft peaks.  Start by mixing the egg whites slowly until foamy.  Then start to beat the egg whites faster, until they increase in volume and stand in peaks that are soft enough for the ends to turn over.  Gradually, whisk in the rest of the sugar to form stiff, glossy peaks.  Carefully stir 2 large spoonfuls of the egg white mixture into the chocolate mixture to loosen the texture, then gently fold in the rest until all is evenly mixed.

Pour the mixture into the spring form pan and bake for about 30-35 minutes, or until a cake tester inserted into the cake comes out clean.  Remove from the oven and let rest in the pan for 10 minutes.  Take out of pan and let cool on a wire rack. 

Carefully peel off the paper lining and transfer the cake to a serving plate.  Garnish with whipped cream and grated chocolate (recipe follows).

Whipped cream
2/3 cup heavy cream
2 oz (60g) semisweet chocolate

Whip cream into stiff peaks.  Place a spoonful on each plate next to a slice of cake.  Grate chocolate using a Microplane Coarse Grater over the cake and whipped cream.  Serves 8.