Preheat the oven to 100°C fan-forced (120°C conventional). Grease two large oven trays. On two baking paper sheets, mark four 4.5cm circles spaced apart. Place the sheets marked side down on the trays.

Beat the egg whites until soft peaks form. Gradually add caster sugar one tablespoon at a time, beating well after each addition until fully dissolved. Add vinegar and cornflour, then beat until glossy and well combined.

Spoon a quarter of the mixture into a piping bag fitted with a 1cm plain nozzle. Pipe small mounds of meringue onto the prepared baking paper, using the circles as guides. Fill another piping bag fitted with a 0.5cm fluted nozzle with the remaining meringue and pipe three rows of small vertical layers around each mound to create the shape of a Christmas tree.

Bake the meringue trees for 50 minutes to 1 hour until the edges are crisp but not colored. Switch off the oven and leave the meringues inside to cool with the door slightly ajar.

Pulse the pistachios in a food processor until finely crumbed.

Beat the thickened cream with icing sugar and rosewater until just firm peaks form. Transfer a quarter of the cream to a piping bag fitted with a small plain nozzle and pipe small rounds onto the meringue trees to help the silver cachous stick.

Decorate with silver cachous, raspberries, and freeze-dried raspberry powder. Sprinkle pistachio crumbs over the top and serve alongside fresh strawberries and the remaining whipped cream.