Preheat the oven to 150°C or 130°C fan-forced. Line 4 baking trays with baking paper or 4 silicon macaron mats.
To make the macaron shells, place the ground almonds and icing sugar into a blender or food processor and pulse until fine, being careful not to overheat the mixture. Pass the mixture through a sieve 2 or 3 times, pushing through any lumps with the back of a spoon.
Measure out half the egg whites and add to the almond meal mixture. Using a spatula, mix until just combined, taking care not to overwork the mixture.
Place the remaining egg whites into a very clean stand mixer bowl. Whisk on a medium high speed until soft, frothy peaks form. Continue to whisk while you prepare the syrup.
Place the caster sugar and 35ml water into a small saucepan and set over a medium heat. Stir the mixture and allow it to come to the boil. Using a sugar thermometer to check the temperature, cook the syrup until it reaches 118°C. Once it has come to temperature and is a syrupy consistency, remove from the heat.
As the egg whites continue to whisk, pour the syrup down one side of the bowl in a slow, steady stream until all of it has been incorporated into the egg whites. Add the pink food colouring to your desired colour and continure to whisk the meringue on high speed until thick and glossy, about 5 minutes. The base of the bowl should be warm but no longer hot.
Add the meringue mixture to the almond meal mixture and, using a clean spatula, fold gently until evenly combined, taking care not to overmix. The mixture should have a soft paste-like texture and a dropping consistency.
Transfer the mixture to a large piping bag fitted with a 1cm round piping tip. Pipe small rounds, about 2cm in diameter, onto the lined baking trays. Help the macaron mixture to level out by tapping the underside of the trays with the palm of your hand.
Set the macarons aside to form a "skin" on top of the shell, about 30 minutes. Once the skin has formed, place into the preheated oven and bake for 12-15 minutes. Once baked, open the oven door and leave ajar for 2 minutes before removing the macarons.
Set the macarons aside on the trays to cool completely. Once cool, lift off the trays with a round-tip palette knife. Set aside in an airtight container until ready to fill.
For the buttercream filling, add the very soft butter to the bowl of a standmixer fitted with a cream paddle and beat until very pale and light in texture. Add the icing sugar, champagne essence, rose essence, rose water and salt. Mix until all the ingredients are incorporated and the mixture is light and creamy.
Transfer the buttercream to a piping bag fitted with a 1cm tip. Pipe the buttercream onto half of the fully cooled macaron shells and sandwich withanother shell.