Preheat the oven to 140°C (275°F), gas mark 1 and line a baking sheet with greaseproof paper.
Whisk the egg whites with the salt in a large clean bowl, either by hand or with a hand-held electric mixer, until very stiff and then gradually whisk in the sugar.
Continue whisking until the mixture is glossy and quite stiff.
Using a large spoon, scoop 6 discs of meringue onto the prepared baking tray. Cook in the oven for 45 minutes.
Turn the oven off but leave the meringues inside for 30 minutes.
Meanwhile, make the praline.
Spread some baking parchment on a baking tray or use a silicone sheet and scatter the pistachios evenly.
Put the sugar and water in a small saucepan and bring to the boil.
When the sugar is boiling and started to turn golden, remove from the heat and leave for about 30 seconds before pouring over the nuts.
Leave to set.
To make the cream, scoop the passion fruit flesh into a bowl.
In a separate bowl, whisk the cream, by hand or using an electric whisk, until it holds its shape, but be careful not to over-whip (you want a syllabub-type texture).
Lightly fold through the passion fruit and icing sugar.
To serve, put a meringue on a plate with a spoonful of the cream and a crumbling of the praline on top.