Preparation

• Adjust the oven rack to the 2nd level mark and preheat your oven to 350ºF. Line two baking sheets with parchment paper or silicone mats.
• In a medium bowl, whisk together the all-purpose flour, baking powder, and salt.
• Using a hand mixer or stand mixer, beat the eggs, egg yolk, granulated sugar, vegetable oil, and vanilla extract together until fully combined and frothy.
• In a small saucepan, heat the semi-sweet chocolate chips and unsalted butter over medium heat until melted. Stir in the unsweetened cocoa powder and espresso powder.
• Pour the melted chocolate mixture into the wet ingredients and mix until just combined.
• Add the whisked dry ingredients and mix on low speed until just combined.
• Scoop the cookie dough onto the baking sheets, leaving about 1 ½ inches of space between them.
• Sprinkle sea salt flakes over each cookie, then bake for 8-10 minutes until the tops are shiny and crackly.
• Remove from the oven and top with additional chocolate chips if desired. Let the cookies cool on the baking sheets for about 5 minutes before transferring to a cooling rack.