Put the chocolate chips into a food processor. Heat the cream and instant coffee until the mixture is very hot, but do not allow it to boil. Pour it into the food processor. Blend for about 1 minute, or until the chocolate is melted.

With the machine running, add the egg yolks one at a time, then the liqueur and brandy. Turn the mixture out into a bowl, and allow it to cool for about 10 minutes. Whip the cream with the sugar and vanilla until the cream is stiff. Fold the whipped cream into the cooled mousse.

Spoon the mousse into champagne or wine glasses, and refrigerate them until the mousse is firm.

Serve the mousse with a little whipped cream on top.