Brown the butter by melting it in a saucepan over medium heat, then cooking until golden brown and nutty, about 5-7 minutes. Cool for 10 minutes.

In a bowl, whisk together flour, baking soda, salt, espresso powder, and Vietnamese cinnamon until well combined. Set aside.

Combine cooled browned butter with granulated sugar and both brown sugars; mix until creamy and light in texture, about 2-3 minutes.

Add the room temperature egg and vanilla extract to the mixture; beat until smooth and well combined.

Gently fold the dry ingredients into the wet mixture until just combined, being careful not to overmix.

Fold in dark chocolate chips carefully to distribute evenly.

Refrigerate the dough for at least 45 minutes to prevent spreading.

Preheat the oven to 350°F (177°C) and line two baking sheets with parchment paper.

Scoop dough onto baking sheets, spacing about 2 inches apart. Bake for 14-16 minutes until edges are light brown and centers slightly underbaked.

Allow the cookies to rest on baking sheets for 10 minutes before transferring to a cooling rack to cool another 10 minutes.