the following recipe, popular around here for the past several years, could be considered as one of those "keepers". part cake, part mousse — it always gets finished quickly and can be served any time of the year, not just at passover. it also contains no matzo meal or matzo cake flour.
the original recipe calls for a little less chocolate than i put but i have found the extra addition helps. it also calls for using chocolate chips. since not all chocolate chips are great quality, i often use the same amount (by weight) with other forms of chocolate [i.e. bars/squares]. you'll have to experiment and see what you like. if you try it using cocoa powder, you'll need to make the conversion as using straight cocoa powder won't work. the recipe also uses margarine to keep it parve or non-dairy. i'm sure you can replace the margarine with butter, if you choose.
there is one thing to consider when making this cake: make sure you use eggs which are extremely fresh. the mousse part of the cake is not cooked and therefore you cannot keep the cake out of the fridge for long periods of time. it is best eaten when served.
also note before starting that the cake is baked in an 8 inch springform type pan which is ungreased. as the cake is not an "unmolded" type one, you will be serving directly from the pan.
easy chocolate mousse cake
1 c (8 oz) chocolate chips or similar chocolate
1/4 lb (1 stick) margarine
1 c sugar
1 tsp vanilla
optional for garnish:
thin chocolate curls or slivered toasted almonds
separate the eggs and place the yolks in one bowl and the whites in another. make sure to use 2 large bowls. if using directly from the fridge, let them sit out to come to room temperature.
in the meantime — in another bowl, either in the microwave with medium low power setting or over a double boiler, melt the chocolate with the margarine. make sure your utensils are completely dry as even one drop of water will make the chocolate seize and ruin everything.
add the vanilla and put chocolate mixture aside to cool.
add only 3/4 c of sugar to the egg yolks and beat them for 5 minutes. make sure to beat them for this long. they should turn whitish coloured and become very thick. set aside.
beat the egg whites until stiff adding the last 1/4 c of sugar slowly by tablespoon (4 tbsp). set aside.
preheat the oven to 325F.
carefully add 1/2 the chocolate to the egg yolks and beat well to incorporate.
repeat with the 2nd half of the chocolate.
in 3 to 4 additions, add the egg whites to the chocolate egg yolk mixture. make sure you have a large enough bowl.
fold the whites carefully and break up any clumps of whites. you may need to use a wire whisk to carefully do this. use a gentle hand so as not to "deflate" all your hard work! this procedure will take a few minutes to do and must be done by hand.
the next part will be a bit of your decision. you need to decide how much cake you want in ratio to how much mousse. i suggest using 4 c (32 oz) batter for the cake and the rest (~ 20 oz) for the mousse. it works out to between 2/3 - 3/4 batter for the cake and 1/4 - 1/3 batter for the mousse.
pour the portion for the cake into the ungreased pan and spread it out a bit so it is even.
bake the cake for 35 minutes. do not open the oven door while baking. place the batter for the mousse in the fridge, covered.
remove the cake from the oven. it will have risen and the surface cracked.
let it sit undisturbed until cooled. the cake will sink — this is normal.
once cooled, pour the mousse into the depression/hole of the cake and refrigerate until serving.
before serving, you can place thin chocolate curls all over the mousse or slivered toasted almonds to garnish.