Preheat the oven to 140°C, 275°F, Gas 1. Line two baking trays with parchment paper. Put the egg whites and the pinch of salt in a large, spotlessly clean bowl and, using an electric whisk or a food mixer with a whisk attachment, whisk until soft peaks form.
Gradually add the caster sugar, one tablespoon at a time, whisking between each addition, until it has all been added and the meringue is satiny and forms stiff peaks.
Using a large spatula or metal spoon, fold in the instant coffee and the toasted chopped hazelnuts.
Spoon the meringue mixture into a piping bag fitted with a 1.5cm nozzle and pipe a series of small rosettes, each approximately 7cm (2¾in) wide, on to the prepared baking sheets. Alternatively, you can use a tablespoon to make rough (rustic!) ‘blob’ shapes.
Bake in the oven for 30 minutes. Test a meringue by lifting it and gently pressing the base — it should be crisp, but give way with a bit of pressure.
The meringues will crisp up more when they are cooling.
For best results, turn off the heat and allow them to cool in the oven with the door slightly ajar.