Brown the butter by melting it in a medium saucepan over medium heat until golden brown and nutty aroma arises, about 5-7 minutes. Let it cool for 10 minutes.

In a separate bowl, whisk together flour, baking soda, salt, espresso powder, and Vietnamese cinnamon.

In the bowl with cooled browned butter, mix granulated sugar, dark brown sugar, and light brown sugar until smooth and creamy, about 2-3 minutes.

Add a room temperature egg and vanilla extract, stirring until smooth and homogeneous.

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

Stir in the dark chocolate chips until evenly distributed.

Cover the dough and chill in the refrigerator for 45 minutes.

Preheat oven to 350°F (177°C). Line a baking sheet with parchment paper. Scoop tablespoons of dough onto the sheet, leaving space between.

Bake for 14-16 minutes until edges are lightly golden. Let cookies rest on the sheet for 10 minutes before moving to a cooling rack.