Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

In a large mixing bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy.

Add eggs one at a time, mixing thoroughly after each, and then incorporate the vanilla extract.

In a separate bowl, whisk together flour, baking soda, and salt, then gradually mix into the wet ingredients.

Fold in the hazelnuts, chocolate chips, and cornflakes gently until fully incorporated.

Scoop rounded portions of dough onto the baking sheets, spacing them 2 inches apart, and bake for 10-12 minutes.

Cool on baking sheets for 5 minutes before transferring to a wire rack to cool completely.