01 -
Preheat the oven to 350°F and line a baking sheet with parchment paper.
02 -
Combine butter and chopped dark chocolate in a microwave-safe bowl. Microwave in 30-second intervals, stirring between each, until fully melted and smooth. Allow to cool slightly.
03 -
In a separate bowl, whisk granulated sugar, brown sugar, egg, and vanilla extract until well combined and light in color to ensure sugar dissolves and achieve crinkly cookie tops.
04 -
Pour the melted chocolate mixture into the sugar and egg blend, stirring until homogeneous.
05 -
Sift and fold in flour, cocoa powder, cornstarch, baking powder, and salt until just combined. Gently fold in optional chocolate chips or chunks if using.
06 -
Using a cookie scoop or spoon, drop rounded 2-tablespoon portions of dough onto the prepared baking sheet spaced 2 inches apart.
07 -
Bake for 8–10 minutes until edges are set and tops show slight cracks while centers remain soft.
08 -
Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.