Preheat the oven to 350°F and line a baking sheet with parchment paper. Set aside.

In a large bowl, use an electric mixer to cream together the butter, light brown sugar, and caster sugar until smooth and fluffy.

Add the eggs, corn syrup, and vanilla extract, mixing until fully incorporated.

In a separate bowl, whisk together 3 ½ cups of flour, salt, and baking soda until evenly combined.

Gradually add the flour mixture to the butter mixture, mixing until a soft dough forms.

Gently fold in most of the chocolate chunks, reserving some for topping.

Slowly incorporate the remaining ½ cup of flour, adding just enough until the dough is soft but no longer sticks to your hands.

Using a kitchen scale, measure out 89-gram dough balls (approximately 2 tablespoons each) and roll them between your palms.

Place 6 dough balls on the prepared baking sheet, spacing them apart to allow for spreading.

Bake for 15 minutes or until the edges are golden brown and the centers are set but still slightly soft.

Immediately after baking, press reserved chocolate chunks onto the tops of the warm cookies.

Let the cookies cool for 5 minutes on the baking sheet before transferring them to a wire rack to cool completely.

Once cooled, enjoy your homemade Costco-style chocolate chunk cookies.