Chocolate Mousse - cooking recipe

Ingredients

4 egg yolks
3/4 cup sugar
6 ounces dark chocolate (semi sweet or bitter sweet)
4 tablespoons coffee
6 ounces unsalted butter
4 egg whites
salt

Preparation

Beat the egg yolks and sugar until it turns into a a thick yellow mixture.
Melt chocolate and coffee in a mixing bowl. (Put the mixing bowl over hot water so that mixing is easier.) Add butter gradually and beat until cream is smooth.
Beat the chocolate with the egg yolks and sugar mixture.
Beat the egg whites and a pinch of salt until stiff.
Sprinkle 1 tablespoon of sugar above and beat again for a two minutes.
Stir about one third of the egg whites into the chocolate mixture. Stir well, then add the remaining whites.
Refrigerate for at least 2 hours. Can be served with whipped cream or custard sauce.