Preheat oven to 180C fan-forced. Line 2 trays with a reusable tray liner.
Use an electric mixer to cream butter, salt, vanilla, and sugars until pale and creamy, scraping down the bowl every so often.
Add the egg and beat for 1 minute or until the egg is fully incorporated.
Sift together the plain flour and baking powder and add this to the creamed butter mixture. Mix on low speed to incorporate, then add the macadamias and chocolate and mix until just combined.
For even-sized biscuits, weigh the dough into 50g portions and roll each into a ball. Place on the prepared tray and flatten slightly. Leave a few centimetres around each biscuit in case they spread during baking.
Bake for 15 minutes or until golden brown - check the bottom of the biscuit by lifting it with a spatula; if it’s golden brown, then the biscuits are ready to be removed from the oven. Allow the biscuits to cool on the tray, then transfer them to a well-sealed jar or container.
