Neoclassic Chocolate Mousse

Heat 2 inches of water in the bottom of a double boiler over medium-high heat.
In a metal mixer bowl (preferably with a handle), or in the top of the double boiler, whisk the eggs.
Gradually whisk in the sugar and water.
With a portable electric beater, beat the eggs over the boiling water on medium speed for 3 minutes.
Increase the speed to high and beat for 4 more minutes.
The eggs should be very thick and pale.
Make sure to keep the beater moving around the whole bowl to ensure that the eggs do not overcook.
Remove from the heat.
Continue to beat on high speed until the eggs cool, about 6 minutes.
Return the bottom of the double boiler to a low heat.
The water should be hot but not simmering.
Put the chocolate and water in another mixer bowl, or in the top of the double boiler (clean), and place over the hot water.
Allow the chocolate to soften and then stir with a whisk until the chocolate and liquid are smooth.
Remove from the heat and whisk or beat in the softened margarine, 1 tablespoon at a time.
On low, beat the chocolate into the eggs.
Spoon into cups or a container and refrigerate.
To use as a filling, beat the cold mousse until it darkens and becomes less spongy.
Spread or pipe onto dessert.
Out of cup, the mousse will be best if eaten within 3 days.
Stirred down and used as a filling, it can keep up to 1 week.
The stirred down version can be frozen for up to 3 months.
Defrost in the microwave on the lowest setting.
Heat in 10-second bursts, stirring in between.