Preheat oven to 180C / 350F /160C fan forced. Line 2 large baking trays with baking paper.
Sift together the flour, cornflour, baking soda and salt.
In a separate bowl, beat together the butter and both sugars until lightened and fluffy.
Scrape down the sides of the bowl and add half the flour mix. Beat until just combined. Add the milk and remainder of the flour and mix until it just starts to come together.
Finally, add the choc chips and macadamias and give the mixture another beat until mixed through and the dough is clumping
Pull the dough together with your hands and then use a medium ice cream scoop to scoop the mixture and transfer to the baking trays. Space the cookies about 1-2 inches apart.
Bake for around 16 minutes, turning the trays halfway through until golden on the edges.
Allow them to cool on the trays for a few minutes before using a spatula to help to transfer them to a cooling rack. Once cool, they will firm up and be crispy on the outside and chewy in the middle