Blanch the pistachio nuts and put them through a meat grinder. Boil the sugar and water for five minutes; when cool, add the coloring, the pistachio nuts, and the gelatin moistened in a little cold water. When this is cold, fold in the cream beaten to a stiff froth, and freeze in a mold.
If this is not too well mixed the cream will separate, which makes the handsomer dessert. When the mousse is turned from the mold it will then have a solid white base with a rather green, beautiful transparent mixture at the top.
This will serve ten persons.