Preheat oven to 180C / 350F /160C fan forced. Line 2 large baking trays with baking paper.
Sift together the flour, corn flour, 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, the remainder of the flour and the oats. Mix until it starts forming big clumps (don’t overmix).
Finally, add the choc chips and hazelnuts and give the mixture another mix on low until just mixed through.
Use a medium ice cream scoop to scoop the dough and transfer to the baking trays. Space the cookies about 2 inches apart.
Bake for around 18 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
Meet the extra chocolate and drizzle over the top then let them set before serving