For the chocolate mousse, break the chocolate into small pieces and melt with the espresso in a water bath. Beat the egg yolks, vanilla sugar and Armagnac until foamy and stir in the liquid chocolate.
Beat egg whites with a pinch of salt and sugar until stiff, whip cream until also stiff and fold both loosely and evenly into the chocolate mixture with a whisk.
Pour the mixture into a large bowl or divide among glasses and place in the refrigerator, well covered.
Use two tablespoons to make dumplings and arrange on large plates.