1¼ cups superfine sugar (sold in most supermarkets)
4 teaspoons instant espresso powder (not instant coffee granules)
4 egg whites
2 teaspoons cornstarch
1 teaspoon white wine vinegar
1¼ cups heavy cream
1 teaspoon good-quality unsweetened cocoa powder
Heat oven to 350 degrees. Line a large baking sheet with parchment paper and, using a 9-inch cake pan as a guide, draw a circle on it with a pencil. (Or you can omit this step and make a freehand circle with the meringue itself later.)
In a small bowl, mix the sugar and espresso powder; set aside.
In a clean, grease-free bowl (preferably metal), use an electric mixer to whisk egg whites with a pinch of salt until they hold soft peaks. (The egg whites won't whip if there is even a trace of grease in the bowl. Wipe the inside with a piece of paper towel dipped in vinegar first, if you want to be extra careful.) Keep whisking while you gradually add the sugar-coffee mixture, 1 tablespoon at a time.
When all the sugar mixture is incorporated and you have a firm, gleaming, ecru-colored meringue, fold in -- using a grease-free metal spoon -- the cornstarch and vinegar. Dollop large spoonfuls of the meringue mixture inside the drawn circle on the parchment paper (or make a freehand circle if you prefer). Smooth and shape meringue with a spatula so it looks rather like the crown of a straw boater hat; it must be flat on top. Put meringue in the oven and immediately turn heat down to 300 degrees. Bake 1 hour, or until the meringue's outer shell is barely crisp.
When it's done, turn off the oven and leave the Pavlova inside to cool. Once the Pavlova is cool, lift it carefully on its paper and place it, top down, on a large, flat plate; gently peel off the paper. Whip the heavy cream until thickened and airy but still soft. Spread whipped cream delicately over the top (which previously was the bottom) of the meringue. With a teaspoon, push the cocoa powder through a fine strainer to decorate -- cappuccino-style -- the top.
"Nigellissima" by Nigella Lawson (Clarkson Potter, 2013)