Easiest Chocolate Mousse by Herve This

From http://www.food52.com/blog/2932_herv_this_chocolate_mousse

Photo by James Ransom

It took a brilliant, adventurous chemist to discover the simplest way to make chocolate mousse at home. Hervé This, the father of molecular gastronomy, discovered how to make a flawless, creamy chocolate mousse out of just chocolate and water.

This all happens fast as the mixture cools, so chances are you'll go too far on your first try. Don't worry — just return it to the pan, melt it, and start over (see step 3). Once you have the rhythm down, you can flavor it as you wish with liqueurs or coffee or spices, sweeten it to your liking, or just keep it dark and intense. In all of these scenarios, a little whipped cream up top is never a bad idea. Adapted from Molecular Gastronomy: Exploring the Science of Flavor (Columbia University Press, 2008)

Serves 4

3/4 cup (6 ounces) water                                                                     
8 ounces chocolate (we used 70% bittersweet — choose a high quality chocolate you love)                                                                     
 
whipped cream for topping (optional)                                                                     

1. Simply pour water into a saucepan (which will be improved from the gastronomic point of view if it is flavored with orange juice, for example, or cassis puree). Then, over medium-low heat, whisk in the chocolate. The result is a homogenous sauce.
   
2. Put the saucepan in a bowl partly filled with ice cubes (or pour into another bowl over the ice -- it will chill faster), then whisk the chocolate sauce, either manually with a whisk or with an electric mixer (if using an electric mixer, watch closely -- it will thicken faster). Whisking creates large air bubbles in the sauce, which steadily thickens. After a while strands of chocolate form inside the loops of the whisk. Pour or spoon immediately into ramekins, small bowls or jars and let set.
   Ask the hotline about this step!
3. Note: Three things can go wrong. Here's how to fix them. If your chocolate doesn't contain enough fat, melt the mixture again, add some chocolate, and then whisk it again. If the mousse is not light enough, melt the mixture again, add some water, and whisk it once more. If you whisk it too much, so that it becomes grainy, this means that the foam has turned into an emulsion. In that case simply melt the mixture and whisk it again, adding nothing.
   Ask the hotline about this step!
4. Serve immediately, or refrigerate. Top with whipped cream if desired