Put a three-quart mould in a wooden pail, first lining the bottom with fine ice and a thin layer of coarse salt. Pack the space between the mould and the pail solidly with fine ice and coarse salt, using two quarts of salt and ice enough to fill the space.
Whip one quart of cream, and drain it in a sieve. Whip again all the cream that drains through. Put in a small pan one ounce of Walter Baker & Co.'s Premium No.1 Chocolate, three tablespoonfuls of sugar and one of boiling water, and stir over a hot fire until smooth and glossy.
Add three tablespoonfuls of cream. Sprinkle a cupful of powdered sugar over the whipped cream. Pour the chocolate in a thin stream into the cream, and stir gently until well mixed. Wipe out the chilled mould, and turn the cream into it.
Cover, and then place a little ice lightly on top. Wet a piece of carpet in water, and cover the top of the pail. Set away for three or four hours; then take the mould from the ice, dip it in cold water, wipe, and then turn the mousse out on a flat dish.