Preheat the oven to 180°C/350°F (160°C fan), and line 2 large baking trays with baking paper.
Add the butter and golden syrup to the Thermomix bowl and melt for 3 min/70°C/speed 2. Meanwhile, mix the bicarbonate of soda in 1 tablespoon of boiling water. When the 3 minutes are up and the butter is fully melted, add the bicarbonate of soda mix to the Thermomix bowl and mix for 5 sec/speed 3.
Add the flour, oats, coconut and sugar and mix for 20 sec/reverse/speed 3. The mixture will come together; use a spatula to scrape down and stir in any bits stuck to the sides of the bowl.
Roll the mixture out into walnut-sized balls and place them onto the baking trays, roughly 5cm apart. Flatten each one slightly with the palm of your hand.
Bake one tray at a time for 12-15 minutes. Depending on whether you like your Anzac biscuits soft or crunchy, 12 minutes = soft, 15 minutes = crunchy. Also, the timing will vary on the oven, so keep a close eye on them.
When ready, remove the biscuits from the oven and cool them on the baking tray for 10 minutes. Then, transfer them to a wire rack to cool completely. They will come out of the oven soft but will harden when cooled.
Notes
Tip: The dough should be easy to roll and flatten without cracking. If it's too sticky, add a little extra flour. If it feels too dry or crumbly, add a little more melted butter.Storage: Store the Anzac biscuits in an airtight container for up to 2 weeks. They can also be frozen for up to 3 months.