6 large egg whites
1½ cups superfine sugar
3 tbs unsweetened cocoa (sieved)
1 teaspoon balsamic vinegar (or red wine vinegar)
2 ounces bittersweet chocolate (finely chopped)
Preheat the oven to 350º and line a baking tray with baking parchment. Beat the egg whites until satiny peaks form, and then beat in the sugar a spoonful at a time until the meringue is stiff and shiny. Sprinkle on the cocoa and vinegar, and the chopped chocolate. Then gently fold everything until the cocoa is thoroughly mixed in. Mound on to a baking sheet in a circle approximately 9 inches in diameter, smoothing the sides and top. Place in the oven, then immediately turn the temperature down to 300º and cook for about one to one and a quarter hours.
When it's ready it should look crisp around the edges and on the sides and be dry on top, but when you prod the center it will feel soft beneath your fingers. Turn off the oven and open the door slightly, and let the chocolate meringue disc cool completely.
When you're ready to serve, move this on the parchment to a tray. Top with whipped cream and seasonal fruits or berries.