Chocolate mousse is not a very complicated dessert to make, but it can sometimes turn into a fiasco. Burnt chocolate, egg white that stays runny, too much sugar... Here's how to avoid mistakes and make a delicious mousse!Choosing the right chocolateTo make a good chocolate mousse, you need to choose suitable chocolate. Choose quality chocolate with at least 70% cocoa, ideally dark chocolate to avoid the mousse being too off-putting. If you use 80% chocolate, your mousse is likely to be very bitter. Use Nestle or Valrhona brands. You can also buy fair trade cocoa in bulk, or in bars in some organic stores.Melting the chocolateTo melt the chocolate, forget the microwave. Instead, you should cook it in a bain-marie, in a bowl over a pan of hot water on low heat. This method of cooking has the advantage of not overheating the chocolate. Remember to stir regularly to help it melt.Sugar... or not!There's nothing more off-putting than a chocolate mousse that's too sweet. It's a common misconception that sugar makes the chocolate taste better, but in reality, it tends to take over. If you use quality chocolate, limit the amount of sugar, or don't use any at all.The importance of eggsTo make the perfect chocolate mousse, you need extra-fresh eggs. Your mousse will hold better, and taste better. The ideal is to use them at room temperature. So take them out at least one hour before cooking them.With or without creamSome chefs suggest a recipe for chocolate mousse made with ganache, which is a preparation of fresh cream and chocolate. If you use this method, your mousse will be more light and creamy. If, on the contrary, you prefer a dense and compact mousse, do not add cream.Beat the egg whites to stiff peaksFor a chocolate mousse to be successful, you have to beat the egg whites until they are stiff. To do this, make sure that your egg whites are free of yolk. If this is the case, remove the yolk using a shell. The whites must be pure.Begin by beating your egg whites with an electric whisk or in a food processor at medium speed. Increase the speed gradually. They should be smooth, firm and shiny. They should then be incorporated into your chocolate mousse with great delicacy so as not to break them.Necessary restIf you thought you'd eat your chocolate mousse as soon as you made it, you're wrong. Chocolate mousse needs rest. It will take a minimum of 2 hours before you eat it to allow it to set properly.A dessert you should eat very quicklyEven if chocolate mousse needs rest, it won't last forever. Like all egg-based preparations, it should be kept for a maximum of 2 to 3 days.Flavour your chocolate mousseTo give a touch of originality without distorting it, there are several things you can add at the last moment, before putting it in the fridge:Tonka beanGinger powderCocoa gritsCoffeeCitrus peelVegan versionIf you go for vegan baking, use the water from the chickpeas and beat them like egg whites. For the quantity, add as much melted chocolate as chickpea water.