Put the coffee powder in the large bowl. Add alittle whipping cream and beat well with a whisk. Pour in the remaining chilled cream and whisk until light. Sprinkle in the sugar in a fine shower, continuing to whisk until the cream is firm, but take care not to overdo it or it will turn into butter. Put in the refrigerator to chill.
Take the two flat discs of meringue, made by piping the meringue mixture in a spiral like a flat snail, and trim them so that they fit inside the soufflé dish. Keep the trimmings and cut the whole meringues into four or five pieces. Fold them with the broken pieces and trimmings into the coffee cream.
Put one of the meringue discs in the bottom of the soufflé dish. Fill the dish with the whipped cream and meringue mixture and cover with the second meringue disc.
Place in the freezer for at least 4 hours. Just before serving hold the base of the soufflé dish under the hot tap for a few seconds and turn out the coffee cream on to a serving dish. Serve with bitter chocolate sauce.