Start by melting 1 cup of unsalted butter in a medium saucepan over medium heat. Stir frequently until the butter transforms into a golden brown with a nutty aroma, typically around 5 to 7 minutes. Remove the saucepan from heat and let the browned butter cool slightly before using it.

In a large mixing bowl, combine the cooled browned butter with 3/4 cup of dark brown sugar and 1/4 cup of white sugar. Beat until smooth and creamy, then add 1 whole egg, 1 egg yolk, and 1 teaspoon of pure vanilla extract, mixing again until fully incorporated.

In a separate bowl, whisk together 2 cups of all-purpose flour, 2 teaspoons of espresso powder, 1 teaspoon of baking soda, and a pinch of salt. This helps blend everything evenly.

Gradually fold the dry mixture into the wet ingredients using a spatula. Combine until no flour streaks remain, then gently fold in 1 cup of dark chocolate chunks.

Wrap the cookie dough in plastic wrap or place it in an airtight container and chill in the refrigerator for at least 30 minutes.

Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper, scoop rounded tablespoons of dough onto the sheet, leaving space between each ball. Bake for approximately 11 minutes.

After baking, allow the cookies to cool on the baking sheet for about 5 minutes, then transfer them to a wire rack to cool completely.