Heat the oven to l50C/300F/Gas2. Line 3 baking sheets with non-stick parchment paper or greaseproof paper. Mark each piece with a 15 cm (7 inch) circle. If using greaseproof paper, lightly brush each circle with oil.

Put the egg whites into a dry, grease-free large bowl. Whisk until stiff and white and standing in firm peaks.

Add the sugar, 1 tablespoon at a time, whisking well after each addition so that the meringue is firm and glossy. Whisk in the instant coffee powder.

Spread the meringue mixture evenly over the marked circles on the baking sheet linings. Bake in the oven for 1 1/2 hours or until crisp and dry in the centre. Swap the top and bottom sheets after 45 minutes to ensure even cooking. Set aside to cool, then peel off lining paper.

Prepare the filling: put the chocolate and water into a small bowl over a pan of simmering water and heat until the chocolate has melted. Stir, then set aside to cool for about 10 minutes or until the chocolate begins to thicken.

Whisk the cream until stiff, then put half of it into another bowl. Stir the chocolate mixture into one half and the instant coffee powder into the other half.

To finish: put 1 meringue round on to a serving plate and spread it with half the coffee cream. Cover with another meringue round and spread with half the chocolate cream. Cover with the third meringue round. Spread the remaining coffee cream over the top and mark decoratively with a fork.

Lightly whip the remaining chocolate cream until stiff. Put the cream into a piping bag fitted with a small star nozzle. Pipe 8 rosettes around the edge of the cake. Sprinkle the rosettes with a little grated chocolate. Serve as soon as possible, or within 2 hours if kept in the refrigerator, otherwise the mocha meringue will lose its fresh, crisp appearance.