Preheat the oven to 120°C, fan 100°C, gas 1/2 and line a baking tray with baking parchment.
In a large, clean glass bowl, whisk the egg whites until firm peaks form. Add the sugar, then fold in the spice; whisk until smooth.
Spoon the mixture onto the baking tray in a wreath shape. Bake for 1 hour, then turn off the oven and leave the wreath in the oven for 3 hours. Transfer to a wire rack to cool completely.
Just before you’re ready to serve, melt the white and dark chocolate in separate heatproof bowls set over – but not touching – gently simmering water.
Whisk together the Greek yogurt, double cream and 2 tbsp of the icing sugar, until medium peaks form. Spoon on top of the meringue.
Put the cranberries in a bowl with the remaining icing sugar and half the lustre. Roll the berries to coat, then scatter them over the meringue. Drizzle over the chocolate and sprinkle over the remaining lustre.
Cook’s tip: use the leftover egg yolks in a homemade custard or mayonnaise.