in double boiler over hot water, melt white chips with liqueur and water; stir gently to blend.
cool until melted white chips mixture no longer feels warm to the touch.
in large bowl with electric mixer, beat cream until soft peaks form; fold cream into melted white chip mixture.
in large bowl with clean mixer, whisk egg whites until soft peaks form.
with rubber spatula, fold egg whites into white chips mixture.
divide mousse among 6 dessert bowls or glasses. chill at least 1 hour.
tips: instead of orange liqueur 4 tablespoons water and 1 teaspoon vanilla extract. 