Preheat oven to 180°C (160°C fan) mark 4. Spread the pistachios out in a roasting tin and bake for 5min to lightly toast. Set aside to cool. Meanwhile, draw an 18cm (7in) circle on a sheet of baking parchment, repeat on 3 more sheets of parchment, then place these on baking sheets.

When the pistachios are toasted, reduce the oven to 160°C (140°C fan) mark 3. Roughly chop 75g (3oz) pistachios and set aside. Add the remainder to a food processor and whiz with 1tbsp of the caster sugar until finely ground – be careful not to over-processor they will be become oily.

Put the egg whites in a large, clean bowl, or in the bowl of a stand mixer, and whisk to stiff peaks. Add the remaining caster sugar, 1tbsp at a time, beating well between each addition – the meringue should return to stiff peaks after each addition. Once incorporated, the mixture should be thick and glossy. Next whisk in the vinegar and vanilla. Fold in the finely ground pistachios using a metal spoon.

Divide the meringue mixture equally among the 4 circular templates on the baking sheets; spread out using the back of a spoon or palette knife to make 4 neat, level circles. Bake for 40min, or until the edges are crisp – the insides should still be gooey. Remove from oven and leave to cool on the trays for 30min before transferring meringues to wire racks to cool completely.

To make the filling: beat the lemon curd in a bowl to loosen to a drizzling consistency, or heat in a microwaveable bowl in short 5sec bursts until runny. Be careful to not let it get too hot – you just want to make it drizzle-able. In a large bowl, whisk the cream and elderflower until it just reaches the soft peak stage – be very careful not to over whip.

Place a meringue on a serving plate and top with a quarter of the cream, drizzle with a little lemon curd and scatter with a quarter of the reserved pistachios. Repeat the layering, finishing with clouds of cream on top, drizzle generously with lemon curd and scatter with the remaining pistachios. Serve.