01 -
Preheat the oven to 350°F and line a baking sheet with parchment paper.
02 -
Combine the unsalted butter and chopped dark chocolate in a microwave-safe bowl. Heat in 30-second intervals, stirring between each, until fully melted and smooth. Let cool slightly.
03 -
In a separate mixing bowl, whisk together granulated sugar, brown sugar, egg, and vanilla extract until the mixture is light in color and fully combined, dissolving the sugar to achieve crinkly cookie tops.
04 -
Pour the melted chocolate and butter mixture into the sugar and egg mixture, stirring until smooth and uniform.
05 -
Sift in the all-purpose flour, cornstarch, unsweetened cocoa powder, baking powder, and sea salt. Gently fold the ingredients together until just combined. If using, fold in extra chocolate chips or chunks now.
06 -
Using a cookie scoop or spoon, drop rounded tablespoons (approximately 2 tablespoons) of dough onto the prepared baking sheet, spacing each about 2 inches apart.
07 -
Bake in the preheated oven for 8 to 10 minutes, until the edges are set and the tops develop slight cracks, while the centers remain soft.
08 -
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.