Melt butter in a 12-inch light-colored skillet over medium heat, stirring occasionally as it cooks. It will go through stages of melting, sputtering (stand back), then it will deepen in color and foam. Underneath the foaming you'll notice browned bits forming and the butter will take on a toasty aroma. It should have a nice golden brown color, not too dark or it's burning (and can taste bitter).

Remove the pan from heat and right away pour the butter into a heat-proof dish (such as a glass 2-cup liquid measuring cup), scraping out any remaining from the pan with a rubber spatula. Cool at room temperature for 10 to 15 minutes, then chill in the freezer for about 45 minutes until cooled (but don't let it get firm and solid or you'll need to re-melt slightly).

In a large mixing bowl, whisk together flour, cornstarch, baking soda, and salt for 20 seconds. Set aside.

Remove butter from freezer and pour into the bowl of an electric stand mixer, using a rubber spatula to scrape out any excess. Add light-brown sugar and granulated sugar to the mixer bowl.

Fit mixer with the paddle attachment and whip on medium-high speed until creamy, about 1 minute. Mix in one egg, then mix in the second egg with vanilla.

Add in dry ingredients and mix on low speed just until combined. Stir in chocolate chips. Make a well in the dough so it chills more evenly, cover bowl and refrigerate for 1 hour. Preheat oven to 350 degrees Fahrenheit during the last 10 minutes of chilling.

Scoop dough out about 2.5 Tbsp at a time (about 45g each) and shape into balls (a bit larger than a golf ball). Place cookie dough balls on parchment paper lined baking sheets (fitting 9 per sheet) and bake in preheated oven for 10-13 minutes until golden but appearing slightly under-baked in the center. Transfer cookie dough that isn't currently baking to the refrigerator to chill until ready to bake.

Allow cookies to cool several minutes on the cookie sheet before transferring to a wire rack to cool. Store cookies in an airtight container.