For the meringue, preheat the oven to 120°C/Fan 100°C/ Gas 1 and line a large baking tray with baking parchment.
In an electric mixer with a whisk attachment, whisk the egg whites until the whites begin to froth and soft peaks form, then begin slowly tapping in the caster sugar, while still whisking.
Keep whisking until the meringue is super thick, then remove the bowl from the mixer. Gradually sift in the icing sugar, folding it in gently and ensuring there are no lumps of sugar left.
Spoon or pipe the meringue onto the baking tray in one single shape and bake for 2 hours, or until slightly coloured and very crisp.
The rest of the Eton mess is very simple. Put half the strawberries in a heatproof bowl with the sugar, lemon zest and scraped vanilla pod, cover tightly with clingfilm and poach over a pan of simmering water for about 30 minutes until the strawberries start to shrivel.
Doing it this way keeps all the flavour in and when you pop that clingfilm open, you get the most miraculous smell!
Remove the vanilla pod and strips of zest and blend a few large spoonfuls of the strawberries in a blender to make a coulis, then put this and the rest of the strawberries in the fridge to chill.
In a large bowl, whip the cream, mascarpone and vanilla seeds to stiff peaks. Add most of the fresh strawberries, hulled and halved, and crumble in nearly all the crunchy meringue.
Pile the cream mixture onto a dish or cake stand and scatter over the poached strawberries, followed by more fresh strawberries, more crunchy meringue and finally the coulis. And there you have it - Eton mess, one of our favourite British desserts!