Popcorn and salted caramel macarons

Method

1. Put the almond meal and icing sugar into a food processor, process the mixture for 30 seconds, scrape down the side, then process again for another 30 seconds. Sieve the mixture into a bowl and set aside.
2. Put the water and sugar in a small saucepan and bring to the boil. Keep an eye on the temperature of the sugar syrup by using a sugar thermometer. Once the temperature reaches 110°C, start whisking the egg whites using an electric stand mixer until soft peaks form. When the temperature reaches 115°C, remove the sugar syrup from the heat, and slowly pour the syrup in a steady stream down the side of the mixing bowl into the egg whites. Increase the speed and whisk the meringue for another 10 minutes until it cools down. It should be smooth and glossy.
3. ‡Remove the bowl of meringue from the mixer. Add half the almond mixture and fold together until well combined, then fold in the remaining almond mixture in two batches. This technique is known as macaronage and is crucial for perfect macarons; the batter should be thick and have a lava-like consistency. Scrape the mixture into a piping bag with an 8 mm round tip.
4. Line a baking tray with baking paper. Pipe the macaron batter onto the tray, about 4 cm in diameter. Once the tray is filled, pick up the tray and give it a gentle tap on the kitchen bench to smooth the top. Sprinkle with the popcorn flakes and set aside for 1 hour to set.
5. Preheat the oven to 140°C. Place the macarons in the oven and bake for 17–20 minutes. Remove from the oven and cool on the tray for 10 minutes, then peel the macaron shells off the baking paper and place them on a wire rack. If the shells stick to the paper, return the tray to the oven and bake for another 10 minutes.
6. To make the salted caramel, put the sugar and water into a saucepan over medium heat and stir until the sugar has dissolved. Then turn the heat up to high and stop stirring; let it boil for about 5 minutes until the sugar starts to caramelise and turn into toffee. Keep an eye on it, as the sugar changes colour rather quickly. Once it reaches a dark golden colour, pour the cream into the hot sugar; be very careful as it will splatter. Keep stirring with a wooden spoon and bring the caramel back to the boil, then add the salt and cook for 3 minutes. Remove the pan from the heat. Whisk the butter, a cube at a time, into the caramel, then pour it into a heatproof jug and set aside to cool.
7. To make the buttercream, beat the butter until pale and creamy. Add the icing sugar, 1 tablespoon at a time, beating until incorporated. Add 2 tablespoons of salted caramel and beat until combined. Scrape the buttercream into a piping bag. Pipe a dollop of buttercream on the flat side of one macaron shell, top with another shell, and press it down gently. Repeat until all the macaron shells are filled.