Rhubarb, rose & pistachio pavlova

1. Preheat the oven to 120ºC, gas mark ½. Put the egg whites and a pinch of fine salt in  the bowl of a freestanding mixer (or in a bowl using electric beaters); whisk until soft peaks form. With the motor still running, gradually spoon in 200g caster sugar until all incorporated. Add the cream of tartar and keep whisking on a high speed for 5 minutes, until the mixture is smooth and glossy. (When you rub a little between your fingers you shouldn’t be able to feel any grains of sugar.) 

2. Draw a 20cm circle on a piece of baking parchment, turn upside down, then stick onto a baking sheet with a dot of meringue mixture on each corner. Spoon the meringue mixture onto the circle and use the back of a spoon to spread it evenly over the circle, creating a slight dip in the centre. Sprinkle over half the pistachios, mostly around the rim, and bake for 1 hour 30 minutes, until crisp and dry on the outside. Switch off the oven, leave the door ajar and allow to cool completely.

3. While the meringue is cooking, put the remaining 150g sugar in a medium-large frying pan with 150ml water. Bring to the boil, swirling to dissolve. As soon as you have a clear syrup (don’t let it colour), stir in the rhubarb and 1 tsp rose water; cook for 2 minutes, then take off the heat. Taste the syrup and add a little more rose water, if liked. Set aside to cool. 

4. When ready to serve, whisk the cream to soft peaks and stir in the yogurt; spoon onto the cooled meringue. Use a slotted spoon to lift the poached rhubarb out of the syrup and arrange it on top of the cream. Decorate with the remaining 20g pistachios and serve with the remaining syrup alongside.