Preheat the oven to 325°F. Line cookie sheets with parchment paper and set aside.

Cut butter into pieces and place in a microwave-safe bowl. Heat on medium heat in 30-second intervals for 2 to 4 minutes until melted. Let cool for 10 minutes.

In a small bowl, mix vanilla, coffee extract and espresso powder until the espresso powder dissolves (see Notes).

In the bowl of a stand mixer (or large bowl and hand mixer), combine brown and white sugars. Pour the butter over the sugars and mix until well combined, about 2 minutes.

Add the vanilla-coffee mixture, eggs and egg yolks, and mix until well combined, about 2 minutes. The batter will be creamy with a caramel color.

Slowly mix in flour, baking soda and salt. Mix until just blended.

Slowly mix in the chocolate chips.

Refrigerate dough for at least an hour before baking. If you refrigerate it much longer or overnight (both are fine) you'll need to leave it out for a half hour or so as it will be too hard to scoop.

Bake for 12-14 minutes. Remove them from the oven when they look almost cooked and the edges are slightly golden, as they will continue to cook a bit on the warm cookie sheet.

Let cookies cool on cookie sheet for about 5 minutes then transfer to racks to cool completely.