A softly, softly approach is the best way to re-create this luscious, velvety French dessert at home.
There are two key methods for making chocolate mousse. The first is the classical French preparation, which entails mixing melted chocolate, butter and raw egg yolks and aerating the mixture with eggwhites and sugar whisked to soft peaks. Whipped cream can be folded through the mousse before it is refrigerated to set. This method is quick and easy, but raw eggs are a cause for concern for some chefs because of the associated potential for food poisoning. As long as the eggs are fresh, undamaged and free of cracks, however, the risk is minimal.
For those who prefer to err on the side of caution, though, this next preparation, adapted from a recipe by Sydney chef Janni Kyritsis, may be more appealing. The idea is to cook the eggs by adding a hot sugar syrup, a technique similar to the one used for making an Italian meringue. First whisk the eggs to increase the volume of air. When the sugar syrup reaches 115C, add it gradually to the egg mixture, whisking continuously so it's evenly distributed. The hot sugar syrup not only cooks the eggs but helps to stabilise them as well.
A great chocolate mousse needs great chocolate. A bittersweet chocolate, which has a high cocoa content of 70 per cent and a complex flavour, will result in a richer mousse. But you can drop the percentage of cocoa solids to 60 or 50 per cent if you prefer a subtler flavour. Avoid chocolate with a lower proportion of cocoa solids, though; it has less setting strength. If the cocoa percentage isn't listed on the packaging, don't use it. Lindt, Valrhona and Callebaut are among our preferred chocolate brands, and they can all be found at select delicatessens and kitchen shops such as Simon Johnson and The Essential Ingredient.
Low, gentle heat is essential when you're melting chocolate. Don't stir very much (or at all) until the chocolate has melted, then stir it only until it's smooth and glossy, lest it split and become grainy. High heat can make chocolate burn and stick, so it's a good idea to melt the chocolate in a bowl placed over a saucepan of barely simmering water. If you're serious about chocolate, a copper bain-marie with a purpose-made ceramic bowl insert from a good kitchenware shop really is hard to beat.
The folding of the mousse mixture is a crucial step. You don't want to lose much air, because it's the air that gives the mousse its light texture. If you're going to add the melted chocolate to your cooked egg mixture in an electric mixer, do it quickly and give the mixture only one or two turns. Any further stirring will deflate the eggs. The other option is to fold the chocolate and egg mixture together with a plastic spatula. Finally, when folding through the cream, the most important thing to remember is to make sure the cooked egg mixture has cooled down to prevent the cream from melting. It's a good idea to use a whisk and rotate the bowl as you fold to incorporate the ingredients quickly, then refrigerate the mousse straightaway so it sets into light, velvety goodness.