Put the egg whites in a clean bowl and whisk until soft peaks form. Slowly add the sugar a tablespoon at a time while continuing to whisk. Once all the sugar has been added, sprinkle in the cornflour and whisk for a few more seconds until glossy.
Line a baking sheet with paper and draw or trace an 8-inch circle. Spread the meringue on top and shape it into a large circle. Make a little crater in the middle for the cream.
Bake for 2 hours, then turn the oven off and let the meringue cool in the oven for a couple of hours (or overnight).
Prepare the topping when you are ready to assemble.
Start with the praline. Heat the sugar in a pan and once it has caramelized, add the nuts and stir it all together. Place a sheet of baking paper on the work surface. Brush some oil on the sheet, pour the caramel on top and try to spread it as thinly as possible. Let it cool completely.
Once cool, break it into shards, and blitz a few pieces to a powder.
Combine the coffee granules with the boiling water and let it cool.
Whisk the cream in a bowl with the icing sugar until it forms soft peaks. Add 2 to 3 tablespoons of the praline powder and fold it all in.
In another pan, heat the chocolate and butter over low heat and stir until melted.
Place the cooled meringue on a serving plate, and top with the coffee cream.
Drizzle the chocolate sauce on top, decorate with the shards and some broken-up chocolate, and serve immediately.