Preheat the oven to 350 and prepare a baking sheet with parchment. Set to the side.
Brown 8 tablespoon of the butter. The butter will melt, turn foam, and then golden brown. Keep an eye on it because it will burn quickly. When done, remove the butter from the heat and pour into a large bowl. Add the remaining 2 tablespoons of butter to cool it down.
When the butter is fully melted, add in the sugars, followed by the egg, egg yolk, and vanilla. Whisk until combined.
Add the flour, cornstarch, baking soda, salt, and espresso powder to the bowl. Fold the dry ingreidents with a rubber spatula, continuing until there are no streaks left in the batter. Fold in the chocolate chips.
Scoop the cookie dough into balls using a medium cookie scoop, baking six at a time. Top the cookie dough balls with chocolate chips before placing them in the oven. Bake the cookies for 8 to 11 minutes.
Let the cookies cool on the cookie sheet for a few minutes before transferring to a cooling rack.
