01 -
Adjust oven rack to just above center position and preheat oven to 350°F. Line two baking sheets with parchment paper or silicone mats and set aside.
02 -
In a medium bowl, whisk together all-purpose flour, baking powder, salt, unsweetened cocoa powder, and espresso powder if using. Set aside.
03 -
In a separate bowl, using a hand mixer or stand mixer with paddle attachment, beat eggs, egg yolk, granulated sugar, vegetable oil, and vanilla extract on medium-high speed until the mixture becomes fully blended and frothy.
04 -
In a small saucepan over medium heat, melt semi-sweet chocolate chips together with unsalted butter, stirring until smooth. Remove from heat and immediately whisk in the dry cocoa powder and espresso powder.
05 -
Pour the melted chocolate mixture into the egg and sugar mixture. Mix until well incorporated. Gradually add the dry ingredients to the wet ingredients, mixing just until the batter is combined.
06 -
Spoon portions of dough onto prepared baking sheets, spacing evenly. Top each mound with additional chocolate chips and a light sprinkle of sea salt flakes if desired.
07 -
Transfer to oven and bake for 8 to 10 minutes at 350°F, or until the tops are shiny and crackled but still tender.
08 -
Allow cookies to rest on the baking sheets for 5 minutes before transferring with a spatula to a cooling rack. Let cool almost completely before serving.