Line 2 baking trays with baking paper. Fit a piping bag with a small(ish), round nozzle (mine was 6mm in diameter) and set aside.
Place the ground almonds and icing sugar into a food processor. Pulse 10 times, then sift into a large bowl, discarding any large lumps. Repeat this process once more, so that you are left with a very fine powder.
Add one of the 36g portions of egg white to the almond/icing sugar mixture, along with 3-5 drops of pink food colouring. Mix well to form a paste with an even, deep pink colour, then set aside.
Place the remaining 36g of egg white into the clean (see Note 2), metal bowl of a stand mixer, fitted with the whisk attachment. Leave aside while you make the sugar syrup.
Place the caster sugar into a small saucepan with the 30ml of water. Place over a medium heat and bring to a boil. Do not stir- swirl gently if necessary. Allow the syrup to continue bubbling, while monitoring the temperature with a digital sugar thermometer.
When the syrup has reached 114°C, turn the stand mixer to high speed and begin to whip the egg whites to soft peaks. Keep the syrup over the heat.
Once the sugar syrup reaches 118°C, the egg whites should have reached soft peaks. With the mixer still running on high speed, carefully pour the syrup down the side of the bowl in a slow, steady stream. Once all of the syrup has been added, turn the mixer up to full speed and beat for 5 minutes, or until stiff peaks are achieved and the metal bowl has come to room temperature.
When the meringue is ready, add 1/3 of it to the pink almond mixture. Mix vigorously to combine the two mixtures and loosen the thick paste.
Add the rest of the meringue and fold it in, using a figure of eight motion, until the mixture is cohesive and comes off the spatula in ribbons- if you leave those ribbons for 30 seconds they should level themselves out into the rest of the mixture.
Transfer the macaron batter to the prepared piping bag. Holding the bag vertically to the baking tray, pipe heart shapes with the batter (see Note 3).
Once the macarons are piped, lift the whole tray and drop it down onto the work surface a few times to bring any air bubbles to the surface. Use a sharp knife/cocktail stick to burst any remaining bubbles, letting the mixture fall back on itself.
Set the macarons aside at room temperature to form a skin- on a relatively dry day, this should take about 30-40 minutes, but can take less time on drier, warmer days and more time on cold, humid days. Check on the macarons every 10-15 minutes or so, if unsure. The macarons will be ready when you can gently touch their surfaces without any batter coming off on your finger.
When the macarons are almost ready, preheat the oven to 165°C fan. When the macarons are ready and the oven is hot, bake the macarons in the centre of the oven, one tray at a time, for 11 minutes. To check if they are done, place a finger on top of the shells and wiggle gently. When done, the tops of the macarons should not wobble. Remove from the oven and allow to cool completely on the tray.