Frozen thandai semifreddo meringue cake

Method

1. Heat the oven to 130°C fan/gas 2. Draw an 18cm diameter circle on 2 pieces of baking paper, then put pencil-side down on 2 oiled baking trays.
2. For the meringues, whisk the egg whites and a pinch of salt with an electric mixer to soft peaks (that flop over when you lift out the whisk). With the motor running on medium, add the sugar gradually and whisk until firm and glossy. Whisk in the vinegar, then gently fold in the cornflour and rosewater using a large metal spoon.
3. Spread a third of the meringue within one of the traced circles, smoothing the top with a palette knife, then pile the remaining meringue in the other circle, forming peaks and swirls on top. Transfer both trays to the oven (lower shelves), then reduce the temperature to 110°C fan/gas 1 and bake for 2 hours until crisp and the meringues feel firm and dry. Turn off the oven and leave the meringues inside with the door closed to cool completely (at least 5 hours or overnight).
4. For the thandai semifreddo, make a thandai paste: put the sunflower seeds, poppy seeds, almonds, pistachios, cardamom and peppercorns in a small bowl. Add the boiling water so everything is submerged, then cover the bowl and leave at room temperature for the nuts and seeds to soften overnight. The next day, whizz to a fine paste in a food processor.
5. For the semifreddo base, set a heatproof bowl over a pan of simmering water (don’t let the base touch the water). Put the egg yolks, sugar, saffron and its soaking water in the bowl. Using an electric mixer, whisk together for 5-6 minutes until the mixture is thick and pale, and holds a thick ribbon on the surface when you lift out the beaters. Remove from the heat and continue whisking until the mixture has cooled to room temperature.
6. In a separate bowl, whisk the 300ml cream to soft peaks. Fold the soured cream, melted white chocolate and thandai paste into the beaten egg mixture, then the whipped cream.
7. To assemble the cake, put the smaller meringue in the base of the prepared cake tin. Spread the thandai semifreddo on top, then cover with the large meringue (don’t worry if the meringues crack). Wrap well, then freeze overnight or until ready to serve (see Make Ahead).
8. About 30 minutes before serving, transfer the cake to the fridge to make it easier to cut and serve. Unmould the cake onto a serving plate. Whip the remaining 400ml double cream to soft peaks, adding rosewater to taste. Pile the whipped cream on top of the meringue cake, then decorate and serve immediately. I like to add a few sparklers for festive glam.