Place the unsalted butter in a microwave safe bowl. Microwave for 20-30 seconds until the butter has melted.
Add the two sugars, vanilla extract, whole egg and egg yolk into the melted butter and mix together until fully combined.
Now fold in the cinnamon, self-raising flour and salt. The mixture will come together to form a cookie dough.
Fold in the white chocolate chips and macadamia nuts (saving a handful of each for later).
Cover the bowl with clingfilm and refrigerate overnight, or for at least 4 hours.
Roll and bake the cookies
Preheat the oven to 180°C (fan oven) and line 2 large, flat baking trays with greaseproof paper. If you only have 1 baking tray you can bake the cookies in batches.
Take the cookie dough out of the fridge and leave to soften at room temperature for 15 minutes.
Scoop up a heaped tablespoon of cookie dough and use your hands to roll it into a ball. Place on the baking tray and do not flatten. Repeat this step until all the cookie dough has been used up. Remember to leave roughly 8-10cm between each ball so they have enough room to spread out.
Bake for 10-12 minutes. The cookies should be golden on the outside but the middle still pale and soft. Don't worry if the middle still looks under-baked, this is how they are meant to be and the cookies will carry on baking as they cool down.
As soon as the cookies are out of the oven, gently push the leftover white chocolate chips and macadamia nuts into the top of each cookie.
Leave on the baking tray for 15 minutes to cool down and firm up. This will change the cookie texture so try to resist the temptation to tuck in straight away.
Notes
Store your cookies at room temp, in an airtight container, for up to 4 days.