Preheat the oven to 200℃ (if fan-assisted, if not set it to 220℃, gas mark 7 or 425℉).
Mix the butter and sugar until fully combined, either in a stand-mixer or with a hand mixer for 5-7 minutes until mixture is paler and light and fluffy.
Mix one egg at a time into the mixture.
Add the flour, cornflour, salt, and bicarbonate of soda and mix until just combined – try not to over mix here.
Add in the milk chocolate and the hazelnuts and again mix until just combined.
Spoon the mixture out onto a plate into 10-12 mounds (don’t compact them down!) and put in the freezer for at least 30 minutes, or overnight.
Remove and cook on a foil-lined baking tray for 8 minutes, then turn the tray around and bake for a further 4 minutes until the tops are light golden.
If you prefer your cookies to be firmer and crispier then put your oven down to 180℃ and cook for 14 minutes (again keep an eye on them and adjust the cooking time to your personal taste).
Allow to cool and firm up on the baking tray for at least 20 minutes, if not longer.
ENJOY!
