Place chocolate, water, and Kirschwasser in a medium size heatproof bowl. Bring 1 inch of water to a simmer in a wide skillet. Turn the heat off and wait 30 seconds. Set bowl of chocolate in pan of water. Stir white chocolate mixture constantly until melted and smooth. Or, melt in a microwave on low for about 2 minutes. Stir until smooth and completely melted. White chocolate is very fragile and burns easily. Do not turn the heat on again under the skillet unless absolutely necessary. Let cool until a dab touched by your upper lip feels slightly cool. Whip the cream until soft peaks form--not too stiff. Carefully fold cream into cooled white chocolate mixture; the mousse will seem very soft. Scrape mold immediately into lined mold. Mousse sets quickly and should not be spread or manipulated too much after it is completed.
Recipe courtesy of Alice Medrich