Cream butter, brown sugar, and granulated sugar until light and fluffy

Beat in egg and egg yolk until smooth

Mix in vanilla extract and espresso powder

In a separate bowl, whisk flour, baking soda, and salt

Gradually add dry ingredients to wet mixture and mix just until combined

Fold in chocolate chips

Cover and chill dough for at least 1 hour

Preheat oven to 350°F (175°C) and line baking sheets

Scoop dough into 2-tablespoon portions and space 2½ inches apart

Bake for 11–13 minutes until edges are set and centers are soft

Cool on baking sheet for 5 minutes, then transfer to a rack