For the meringue: Firstly, preheat the oven to 145C/120C Fan/Gas Mark 1. In a large bowl, fitted to a stand mixer, add the 95g egg whites. Then mix together the caster sugar and water in a small saucepan, then place over a high heat and bring to the boil. Using a sugar thermometer check the temperature of the sugar syrup. Once this has reached 110C, start whisking the egg whites on a medium speed until they’ve reached soft peaks. Once the sugar syrup has reached 120C (and the egg whites are at soft peaks), take off the heat and pour the syrup down the side of the bowl being careful not to splash yourself. Then whisk on full speed for 5 minutes, until the meringue is glossy and thick, and the bowl is lukewarm to touch.
For the paste: Whilst the meringue is whisking, blend together the ground almonds and icing sugar in a food processor until fine. Then sieve twice into a large bowl and discard any chunks. Add the 95g egg whites and combine thoroughly by hand. Then add your food colouring in – noting that the colour will get lighter once you add the meringue.
Then add the meringue in three stages: 1st stage – fold one third in fairly vigorously, until well combined.2nd stage – fold the second third in gently.3rd stage – fold the final third in very gently. Then add the mixture to a piping bag and snip off the end to create a 1cm wide hole. Line a large baking tray with baking paper, and pipe circles roughly 3-4cm wide with a 2cm gap between each. Then heavily drop the baking tray 3 times onto your work surface to remove any air bubbles and bake immediately for 19 minutes. Leave to cool on the trays for 5 minutes, before sliding the baking paper onto a cooling rack. Once the shells are almost finished baking, pipe your next tray ready to put into the oven. Continue this process until all the mixture is used - you will need to pipe 60 shells to create 30 macarons. Then set all aside to cool.
For the apple compote: Peel, core and chop the apples into small chunks and place into a saucepan. Then add the butter, water, caster sugar, cinnamon stick, lemon juice and stir to combine. Place over a medium heat and cook, stirring frequently, breaking up the apples as they start to soften. Keep cooking until the apples start to caramelise, then take off the heat. Discard the cinnamon stick, then mash the apples until they are completely broken down. Then spread onto a plate to cool and set aside.
For the buttercream: Place the butter into a medium bowl and beat using an electric hand-whisk until lightened in colour and creamy. Then add the icing sugar and beat on a low speed until combined. Then increase the speed and beat until light and fluffy. Finally, mix in the salted caramel sauce until well combined. Then place into a piping bag.
To assemble: Pipe a ring of buttercream around the outer edge of half of the macaron shells, then fill the holes with the apple compote. Finally, sandwich with the remaining macaron shells.