Preheat your oven to 325°.
Line a baking sheet with parchment paper and set aside.
Melt butter half way in the microwave.
In the bowl of your stand mixer cream the butter with both of the sugars until smooth. Add in the egg, egg yolk and vanilla and mix until completely combined. Incorporate the flour, corn starch and baking soda on low until JUST combined.
Fold in chocolate chips by hand with a rubber spatula or spoon until they are evenly distributed.
Shape dough into 1-2 inch balls, a little bit higher than normal (more like an oval - refer to picture in post).
Place on prepared baking sheet 1-½ in. apart and bake for 11-12 minutes.
Don't over-bake! Cookies may seem to be underdone, but they aren't. They will firm up as they cool.
If you prefer a cookie with crunchy edges, bake for a few extra minutes.