In a small mixing bowl, combine Nutella, margarine and sugars. Using a spoon and/or spatula, mix until evenly combined.
Add egg yolk and mix well.
Add in flour, baking soda and cornstarch and mix just until there’s no more streaks of flour.
Add in chocolate chips and gently fold in.
Form dough into 1 to 1 1/2 inch balls and place onto lined cookie sheet at least 1 1/2 inches apart. Flatten them a little with the spatula or the back of a spoon. You may add some more chocolate chips on top like I did.
Place cookie sheet inside the ref and then preheat the oven to 350° F / 176° C / 160° C (for convection or fan-forced ovens like mine).
After 10-20 minutes (preheating should be done by this time), remove cookie sheet from the ref and place inside the oven.
Bake the cookies for 10 minutes. The cookies would be puffed up and look still wet, but that’s exactly what you’re aiming for. They’d deflate and crinkle a bit while cooling.
Remove from the oven and cool on the cookie sheet for 5 minutes. Then, transfer to wire rack to cool completely.
Recipe Notes
This is a small-batch recipe; just about perfect for impromptu cravings or when you don’t need to bake a whole lot of cookies.
The original recipe called for butter but I’ve run out so I used Baker’s Best margarine instead.
There was supposed to be salt in here somewhere, but the margarine I used was already quite salty so I just skipped it altogether.
The cornstarch is very important. It’s what makes the cookies chewy.