Start by creaming the butter. Then add the sourdough discard and mix.
Add the brown sugar to the butter mixture and cream until fluffy.
Add the egg, egg yolk and vanilla.
In a seperate bowl combine the flour, corn starch, salt, and baking soda.
Add the flour mixture to the the butter. Mix until flour is just incorperated.
Add the chocolate chunks and mix.
Scoop cookies using about 3T per cookie onto a parchment line cookie sheet. Refrigerate for at least 30 minutes.
While cookies are in the fridge preheat oven to 375℉.
Once at least 30 minutes have passed remove some cookies to a separate parchment (or slipmat lined) cookie sheet. Bake 14-16 minutes until edges just start to brown.
Remove from oven and allow to sit on cookie sheet for 10 minutes before removing to a cooling wrack.
