Preheat your oven to 200ºC.

Line a baking tray with baking parchment and  pour in the caster sugar and heat it in the oven for 7 minutes.

Heating the sugar helps to create a glossy, stable mixture. It will start to crystalize slightly on the edges.  Then you will know it is ready.

Pour the egg whites into a mixer and whisk them slowly, allowing small stabilising bubbles to form, and then increase the speed until the egg whites form stiff peaks.

Remove the sugar from of the oven, and get the oven temperature down to 100ºC (leave the door open to help speed this up.)

 Slowly spoon the hot sugar into the beaten egg whites with the mixture on a high speed, making sure the mixture comes back up to stiff peaks after each addition of sugar. 

Once  all the sugar, is added continue to whisk on full speed until the mixture is smooth, stiff and glossy .

Continue to whisk for at least 5 minutes after all the sugar has been added. Test by rubbing a bit of the mixture between your fingers; if you can still feel the gritty sugar, keep whisking at full speed until it has dissolved and the mixture is smooth, stiff and glossy.

Add a few drops of Rosewater and taste.  Add more if necessary.

Spoon the mixture into a piping bag or put spoonfuls onto the prepared baking tray.

Add slithered Pistachios.  Do not add too many as the oil from the nuts can make the mixture go flat.

Bake for about 35-45 minutes or until the meringue bases come off the baking paper cleanly.