Cake 7: Chocolate Mousse Cake

This week was supposed to be tiramisu, but the mascarpone did not arrive on time, so we made the next week's cake instead. Class started off with Chef demonstrating the japonais biscuit. It's basically a cookie made from a nut meringue. She beat egg whites until soft peaks, then added corn starch, icing sugar and ground almonds. The batter was then piped into several 6" discs, letting the batter fall from the tip while trying to make the layer relatively thick. The leftover was piped into small mounds to be used for decoration.

Next, we started on the mousse. I melted couverture chocolate and butter over a bain-marie, while my partner whipped the cream. Then I heated eggs and sugar over hot water to make a “cheater's” version of pâte à bombe. Here is where I made a mistake: I turned the heat too low and the eggs never got hot enough. When we whipped it in the mixer, the mixture foamed but didn't thicken. Our instructor said the mousse would still turn out though. Finally, we combined the egg and chocolate mixtures, whisked in dissolved gelatin and then the whipped cream. Each mixture was tempered with the next ingredient so that it would incorporate evenly.

As I forgot to bring my springform ring, I borrowed my partner's 5" one and ended up making a tiny cake. We trimmed the baked japonais discs so that it was slightly smaller than the ring. One went in the bottom and mousse was poured over top. Another layer of biscuit, then more mousse. As I should have learned from making a mousse cake last week, it's important to trim the cake layer enough so that the mousse can run down the sides. Otherwise, when the cake is unmolded, there will be a hole. We levelled off the tops, leaving it slightly mounded as the mousse tends to sink as it sets. The cakes then went into the freezer.

When we came back from the break, Chef demonstrated how to garnish the cake. She made up a chocolate glaze using couverture chocolate, coating chocolate, glucose, cream, water and sugar. The coating chocolate has had the cocoa butter removed and replaced with more stable tropical oils. Glucose helps to prevent crystallization. The glaze was poured over the chilled cake and she quickly masked it. The small cookies were pressed around the sides, and she did a simple white chocolate pattern on top. Since we were out of time, I ended up taking some coating chocolate coins and making the glaze at home, substituting corn syrup for glucose.

The cake has excellent chocolate flavour and is quite rich, despite the airiness of the mousse. The japonais biscuit in the cake softened and became a little chewy but the cookies used for garnish were still a bit crispy.