Preheat the oven to 350 degrees F and line a baking tray with parchment paper.

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 over the cocoa and vinegar, and the chopped chocolate. Then gently fold everything until the cocoa is thoroughly mixed in.

Mound the meringue mixture onto 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 F 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 you should feel the promise of squidginess 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, invert on to a flat-bottomed plate. Whisk the cream till thick but still soft and pile it on top of the meringue. Scatter the strawberries over the cream. Coarsely grate the chocolate over the top of the strawberries.