Chocolate Mousse

Combine semisweet chocolate, unsweetened chocolate and milk in heavy small saucepan. Stir over low heat until chocolates melt. Mix in the Grand Marnier or vanilla, if desired. Let chocolate mixture stand until cool to the touch yet still fluid (if chocolate is not cool enough, it will seize into tiny flecks when folded into the whipped cream).

Using an electric mixer, beat the heavy cream and sugar in a large bowl just until stiff peaks form (do not overwhip or you'll end up with butter). Using whisk, fold some chocolate mixture into the whipped cream. Then, add remaining chocolate mixture and fold until just combined. Spoon chocolate mousse into 6 wine goblets or ramekins, and chill. (Can be made 1 day ahead.)

If desired, spoon or pipe sweetened whipped cream atop the mousse just before serving.