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 after each, until smooth and fully melted. Let cool slightly.
03 -
In a large bowl, whisk together granulated sugar, brown sugar, egg, and vanilla extract until pale and well combined to dissolve the sugars and create a light texture.
04 -
Pour the melted chocolate and butter mixture into the egg and sugar bowl, stirring until smooth and uniform.
05 -
Sift in all-purpose flour, cornstarch, cocoa powder, baking powder, and salt. Gently fold until just combined. If using additional chocolate chips or chunks, fold them in now.
06 -
Using a cookie scoop or spoon, drop rounded tablespoons (approximately 2 tablespoons each) of dough onto the parchment-lined baking sheet, spacing them about 2 inches apart.
07 -
Bake in the preheated oven for 8 to 10 minutes or until edges are set and tops have 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.