This is the best chocolate cake I've ever eaten! Something between a mousse and a cake, it is so moist it will melt in your mouth like a chocolate bar. I tried about 7 different flourless chocolate cake recipes before I came up with this one which incorporates only the best of them all. This cake will only be as good as the chocolate you use, so make it good! If you are on a no-flour diet (for celiacs for instance) this cake is perfect- just use sweet rice flour to flour the pan instead of wheat flour. For an exotic treat, add 2 tsp key-lime zest or 2 tsp key-lime extract along with the vanilla extract. Cooking time does not include chilling time.
06In a clean mixing bowl (make sure there is no oil residue on the bowl or mixer attachments) beat the egg whites until they become cloudy and frothy; about 30 seconds.
07Continue beating while adding the brown sugar and cream of tartar.
08Beat until stiff peaks form- be careful not to over beat--this is most important!
09If the eggs curdle, throw them away and start over with new egg whites, seriously.
10Whisk the egg yolks and vanilla into the melted chocolate mixture in a large mixing bowl.
11Gently fold the egg whites into the chocolate (start by folding in about 1/3rd of the whites, then gently fold in the remaining whites), the mixture should end up fluffy and light.
12Pour into the prepared pan.
13Wrap the bottom of the pan with foil and place the pan in a deep cooking sheet with about 1/2 to 1 inch of water in it.
14Bake the cake for about 60-70 minutes or until it passes the toothpick test.
15Remove cake from oven and allow to cool for about an hour.
16Gently run a knife around the edge of the pan, and then carefully invert the cake onto a flat plate or other surface.
17Remove the paper from the bottom (now the top) of the cake.
18Invert again onto the final plate for displaying the cake.
19The cake can be eaten right away but it may fall slightly when it is cut- for best results, it should be refrigerated for at least 6 hours before serving.