Preheat the oven to 350F, then line a baking sheet with parchment paper or silpat.
In a medium bowl, cream the butter and both sugars together. I did so using my spatula.
Add in the vanilla and egg yolk and mix everything is smooth and well incorporated.
Add in the dry ingredients over the wet ingredient mixture, starting with the flour, corn starch, baking soda, and salt. Stir just until combined.
Fold in the chocolate chips, then using a medium cookie scoop, scoop our the cookie dough to create 10 equal cookies.
Place them on the prepared baking sheet and bake for 9-10 minutes. Don't worry if they look underdone or gooey in the middle. That's what we want, they will continue to bake even after you pull them out of the oven to cool.
Cool on the cookie sheet for 5 minutes then transfer to a cooling rack.