Raspberry Sandwich Meringues

Combine all ingredients in a metal bowl and place the bowl over a bain-marie (making sure it doesn't touch the water). Whisk gently and continuously with a hand whisk over low heat until the sugar dissolves in the liquid (test by rubbing between your fingers). Then remove from the steam and transfer to a stand mixer bowl. Begin whisking at a low speed (level 2 out of 6). Gradually increase the whisking speed after a few minutes, and after a few more minutes, increase to maximum speed and continue whisking for several more minutes. The meringue should be beautiful, white, glossy, bubble-free, and form soft but stable peaks, and it should no longer be warm. If it's still warm, it must cool down before piping.

Pipe onto baking paper on a prepared baking sheet using your chosen nozzle, leaving at least 2-3 cm between each meringue, and top with halved pistachios.

Bake in a fan-assisted oven (if you have a gentler fan setting, use it) at 90°C, you can bake two trays at once, for 2 hours and 15 minutes (if piping larger meringues – e.g., rosettes – bake for 2.5 hours). Do not open the oven door and leave the meringues in the switched-off oven for at least another hour.