Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius). Line baking sheets with parchment paper or baking mats, and set aside.
Place butter in a microwave-safe bowl and heat for 30-45 seconds (full strength) or until it's almost completely melted but has a few soft pieces left.
In a large mixing bowl, whisk together flour mixture, baking soda, cornstarch, and salt.
In the bowl of a stand mixer (or a large mixing bowl with a hand mixer), beat together butter, sugars, and vanilla for 1 minute. Add the eggs one at a time, mixing in between additions. Turn the mixing speed to low and gradually add in the dry ingredients. Beat until just combined or until a soft dough forms. Fold in the chocolate chips with a spatula. Now you can either bake the dough straight away, chill for 3 hours, and bake, store it in the refrigerator for up to 5 days, or freeze it.
To bake the cookies, use a standard-size cookie scoop (approximately 1.5 tbsp.) to form balls of dough. Place onto the prepared sheets, leaving at least 2 inches in between. Sprinkle with sea salt if desired.
Place in the oven and bake for 11-13 minutes, rotating the sheet halfway through the baking process. Remove from oven when cookies are golden brown in color around the edges. Let cookies cool on the pan for 3-4 minutes, then transfer to a wire rack to cool completely.
Notes
Recipe Source: Adapted from The Back In The Day Bakery Cookbook- I prefer using a mix of semisweet chocolate chips and bittersweet chocolate chips. Ghirardelli is my brand of choice.- Cookie dough can be wrapped or placed in an airtight container and stored in the refrigerator for up to 5 days or can be portioned and frozen for up to 3 months.To STORE baked cookies, place them in an airtight container at room temperature for up to one week. FREEZE the dough or baked cookies for up to three months.To REHEAT, place cookies in a preheated oven at 300°F (150°C) for 5-7 minutes or microwave for 10-15 seconds. For frozen dough, bake directly from the freezer, adding an extra minute to the baking time.