Preheat oven to 350°F (175°C). Line baking sheets with parchment paper
Add butter to a skillet over medium heat and cook for 5-10 minutes; until the butter begins to brown. Remove from the heat and let cool for about 5 minutes or until cool
In a large bowl, mix the brown butter, brown sugar, granulated sugar, and espresso powder. Set aside
In a medium bowl, whisk flour, baking soda, and salt
To the first bowl including butter and sugar, add egg, egg yolk, and vanilla. Stir until smooth and well combined
Gently fold in the dry ingredients until just combined. Stir in chocolate chips
Roll the dough into 1-tablespoon size balls and place on the baking sheet
Bake for 9–11 minutes, or until edges are golden and centers are slightly soft. Let cookies cool. Enjoy!
