Place the cold, diced butter into a stand mixer and beat briefly until it begins to soften and break into smaller pieces.
Add both sugars and continue mixing until the mixture looks light, creamy, and fully combined without noticeable chunks of butter.
Mix in the eggs and vanilla extract, pausing to scrape down the sides of the bowl to ensure everything is evenly incorporated.
In another bowl, combine the flour, baking soda, cornflour, and salt. Slowly add the dry ingredients to the wet mixture, stirring just until the dough comes together. Be careful not to overwork the dough.
Divide the dough into large portions, roughly 100g each, and roll or shape them into tall balls to help create thick bakery-style cookies.
Cover the dough and place it in the freezer for a minimum of 1 hour before baking.
Bake at 375°F until the edges turn lightly golden while the centers remain soft, around 14–16 minutes.
Leave the cookies on the baking tray for 15–20 minutes after removing them from the oven so they can firm up while staying soft and chewy in the middle.
