Brown the butter by melting it over medium heat in a light-colored pan until the solids turn golden and a nutty aroma develops. Transfer to a heatproof bowl and let cool for 5 to 10 minutes.

Combine the cooled browned butter with the brown sugar and white sugar in a mixing bowl, stirring until mostly combined and smooth.

Stir in the vanilla extract until evenly distributed.

Whisk in the eggs one at a time until just combined. If using espresso powder, fold it in at this point.

Stir in the baking soda and cornstarch for 1 to 2 minutes until dissolved.

Add the flour in roughly one-cup increments, folding gently after each addition until the dough comes together and feels like firm playdough. Avoid overmixing.

Fold in the chocolate chips using a spatula or your hands until evenly distributed.

Line a baking sheet with parchment paper. Using an ice cream scoop, portion the dough into evenly sized mounds, leaving space for spreading.

Preheat the oven to 375°F (190°C). Bake for 11 to 12 minutes until edges are golden and centers look slightly underbaked.

Remove from the oven and gently press a drinking cup over each cookie to flatten slightly while still warm. Let cool on the sheet for a few minutes before transferring to a wire rack to finish cooling.