Place butter in a medium-sized saucepan (preferably a light colored one--this will make it easier to tell once your butter has browned) and melt the butter over low/medium-low heat.

Once melted, increase stovetop heat to just above medium heat. Swirl and scrape the sides of the pan constantly with a wooden spoon or heatproof spatula - butter will foam and pop. Once the this noise slows, you should notice brown bits beginning to form on the bottom.

Once you notice browning (and you smell that beautiful nutty aroma of browned butter), remove from heat quickly and pour into a large, heatproof bowl. Allow butter to cool at room temperature until no longer warm to the touch before proceeding with the recipe.

Once your butter has cooled, add sugars and stir well. Add eggs and vanilla extract and stir until dough is uniform.

In a separate, medium-sized bowl, whisk together flour, cornstarch, baking powder, baking soda and salt. Gradually add the flour mixture to butter mixture, stirring until ingredients are completely combined. Add chocolate and stir well so that chocolate is well distributed through the batter.

Cover cookie dough bowl with plastic wrap and chill in the refrigerator for at least 30 minutes. About 15 minutes before dough has finished chilling/before you are ready to bake, preheat oven to 350F and line cookie sheets with parchment paper. Once dough has finished chilling scoop by about 2 Tablespoon-sized portions. Gently roll the dough between your palms so that you have a round ball, then place cookie dough at least 2" apart on prepared cookie sheet.

Bake at 350F for 10-12 minutes or until edges are just beginning to turn golden brown (cookies should still be quite soft when you remove them from the oven, and may even appear slightly underbaked in center).

Let cookies cool for about a minute then sprinkle lightly with flaky sea salt. Allow cookies to cool completely on baking sheet before removing, then enjoy!