In a large bowl, whisk together flour, cornstarch, baking powder, baking soda, and the 1.5 teaspoons sea salt, set aside.
In a large mixing bowl, using a hand mixer or a stand mixer, cream the butter, sugars until light and fluffy, about 3-4 minutes. Add the vanilla extract, then the eggs one at a time, mixing after each addition.
With mixing speed on low, gradually add the dry ingredients, mix until just combined.
Fold in the chocolate chips, chocolate chunks and any "shavings" you may have created while chopping the chocolate. Place the dough into an air-tight container and chill for 3 hours, preferably 24. The longer the dough chills, the better it tastes. I chilled mine for 72 hours.
When ready to bake, preheat oven to 350 degrees. Line baking sheets with parchment paper or baking mats, set aside.
Using a standard size cookie scoop (1.5 tablespoons) place dough onto the prepared baking sheets (12 per sheet). Sprinkle the tops with a little sea salt, then place in the oven to bake for 10-12 minutes or until golden brown on the edges and lightly golden brown on the tops. The cookies should look a little soft in the centers but should not be doughy. Remove from the oven and allow to cool for 5 minutes on the sheets before transferring to a wire rack to cool completely.