Preheat the oven to 150°C/300°F/regulo 2.
Mark two 7½ inches (19 cm) circles on silicone paper on a prepared baking sheet.
Check that the bowl is dry, spotlessly clean and free of grease. Put the egg whites into the bowl and add 4 ozs (110 g/1 cup) icing sugar all at once; whisk until the mixture forms stiff, dry peaks, 10 minutes approx. Sieve together the cocoa and the remaining ½ oz (15 g) icing sugar and fold in very gently. Spread and bake immediately in the preheated oven for 45 minutes or until just crisp. Allow to get completely cold then peel off the paper.
Meanwhile, very gently melt the chocolate with the rum and 1 tablespoon of cream in a very cool oven, or in a bowl over simmering water. Cool and then fold the mixture into the softly whipped cream; don’t stir too much or it may curdle.
Sandwich the two meringue discs together with Chocolate and Rum Cream and decorate with chocolate wafers.