Whisk together the flour, baking soda, salt and cornstarch in a medium bowl then set aside.
Step 2
In a small pot, melt butter and let it cool slightly. Transfer it to another bowl and whisk it with both sugars until combined. Add the egg and vanilla and whisk again.
Step 3
Add dry ingredients into the wet ingredients and mix until a thick dough has formed. Fold in the chocolate chips and chopped Kinder Bueno bars.
Step 4
Transfer the batter into a pan and bake for 15-20 minutes until golden. Remove from the oven and cool for 10 minutes in the pan then transfer to a rack to cool completely.