#1 Preheat oven to 350°F (175°C). Line baking sheets with parchment paper #2 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 #3 In a large bowl, mix the brown butter, brown sugar, granulated sugar, and espresso powder. Set aside #4 In a medium bowl, whisk flour, baking soda, and salt #5 To the first bowl including butter and sugar, add egg, egg yolk, and vanilla. Stir until smooth and well combined #6 Gently fold in the dry ingredients until just combined. Stir in chocolate chips #7 Roll the dough into 1-tablespoon size balls and place on the baking sheet #8 Bake for 9–11 minutes, or until edges are golden and centers are slightly soft. Let cookies cool. Enjoy!