Set out your butter and eggs so they can come to room temp. If you don’t have the time or patience like me, stick the butter in your pockets and the eggs in warm (not hot) water.

Brown the butter: in a saucepan, over medium heat, melt the butter and stir constantly with a whisk (or spatula) until it starts to turn brown and give off a nutty aroma. Keep an eye on it because it can burn quickly. This takes around 5 - 7 minutes. As soon as it starts to change color, turn off the heat and transfer to a heat safe bowl so it can cool down. Don’t forget all the brown bits from the pan, those are the toasted milk solids. Cool for 15 minutes.

Add the egg, egg yolk, and vanilla, then mix to combine.

In a large bowl, prepare the wet mixture: start by creaming your brown sugar, granulated sugar, and brown butter. Use a hand mixer or a whisk to beat on medium speed until light and fluffy (you know it’s ready if you pinch the mixture between two fingers and feel little to no sugar granules).

In a separate bowl, whisk together your dry ingredients: flour, cornstarch, baking soda, and salt.

Add half of your dry ingredients into your wet mixture. Fold slowly with a spatula and then add the other half of the dry ingredients. While the dough still has some streaks of white flour, add in your chopped chocolate and chocolate chips. Continue folding and stop when combined. Don’t overmix or your cookies will turn out dense.

Scoop your cookie dough into 3 - 4 oz size balls (or your preferred size) and place into a bowl or on a baking sheet. Cover in plastic wrap and chill for 24 hours, or at least 1 hour. Chilling helps the flavors of the cookie develop and prevents overspreading in the oven. If you chill them longer than an hour, let them sit 10 minutes at room temp before baking.

Preheat oven to 350 °F. Place the cookie dough balls onto two parchment paper lined baking sheets, keeping them a few inches apart. Bake for 8-11 minutes. Do not overbake the cookies, the centers will look underbaked but will continue to cook on the hot baking pan. You know they are ready once the edges and bottoms are golden brown.

Let cool for 5 minutes and transfer to a wire rack to continue cooling. Add sea salt if desired. Enjoy with cold milk!