In a large bowl, whisk the flour, baking soda, cornstarch, and salt together in a large bowl. Set aside.

In a medium bowl, whisk the melted butter, brown sugar, and granulated sugar together until no brown sugar lumps remain. Whisk in the egg, then the egg yolk. Finally, whisk in the WR Double Oaked.

Pour the wet ingredients into the dry ingredients and mix together with a large spoon or rubber spatula. The dough will thick and buttery. Fold in the chocolate chunks.

Cover the dough and chill in the refrigerator for 2-3 hours or up to 3-4 days. Chilling is mandatory. The longer you let the dough chill the less spreading you will have during the baking process.

Take the dough out of the refrigerator and allow to slightly soften at room temperature for 10 minutes.

Preheat oven to 325°F (163°C). Line two large baking sheets with parchment paper or silicone baking mats. Set aside.

Roll the dough into balls, about 3 Tablespoons of dough each. Roll the cookie dough balls to be taller rather than wide, to ensure the cookies will bake up to be thick.

Bake the cookies for 12-13 minutes. The cookies will look very soft and underbaked. They will continue to bake on the cookie sheet. Sprinkle the cookies with the Kosher salt.

Allow to cool on the cookie sheet for 10 minutes before transferring to a wire rack to cool completely.