For the meringue, preheat the oven to 140C/280F/Gas 1. Line a large baking sheet with baking parchment.
Place the egg whites in a large, clean bowl. Sift the icing sugar and the instant coffee into the egg whites.
Whisk the egg whites with an electric hand whisk until soft peaks form when the whisk is removed. Add the caster sugar, a little at a time, while continuing to whisk. Whisk until all the sugar is added and the mixture is glossy and thick and stands in peaks when pulled up by the whisk.
Spread the meringue mixture out into a circle on the lined baking tray (alternatively you can make four smaller merinuges) and smooth the top with a palette knife.
Transfer the tray to the oven and bake for 45-60 minutes until crisp on the outside, then turn off the oven and leave to cool with the door ajar for at least 30 minutes. Remove from the oven and peel off the paper.
For the passion fruit cream, gently fold the passion fruit into the whisked cream. Stir in the icing sugar.
To assemble the meringue, cover the meringue base (or bases) with the passion fruit cream. Top with the summer berries and serve.