One of the most important part of this recipe is the melting of the Chocolate - and it is important to get it right to get the best mousse texture. Chocolate is very sensitive to heat and can very easily burn, which will result in a mousse with a grainy texture. The best way to melt Chocolate is over a "Bain-Marie" or "Double Boiler". This technique allows to melt the chocolate slowly and without too much heat. To melt chocolate over a double boiler, add a little bit of water to a small pot and place it on low heat. Place the chopped Chocolate (or chocolate chips/callets) in a heat-proof bowl large enough to stand over the pot. Make sure the bottom of the pot is not touching the water, then leave to slowly melt, occasionally stirring.