Place the chopped semi-sweet chocolate into a microwave-safe container. Warm in short bursts of 20–30 seconds, stirring well between intervals until fully melted and glossy. Set aside to cool slightly.

In a mixing bowl, cream the softened salted butter with both the brown and white sugars until smooth and fluffy, approximately one minute using an electric mixer. Blend in the room temperature eggs and vanilla extract until the mixture becomes silky and homogenous. Stir in the melted chocolate until well integrated.

Position a fine mesh sifter over the bowl and add the all-purpose flour, cocoa powder, baking powder, espresso powder, and salt. Sift directly into the wet mixture. Mix gently on low speed to avoid flour spillage and stir only until just combined.

Incorporate about half of the chocolate chips into the dough using a rubber spatula, reserving the rest for topping the cookies after baking.

Transfer the dough to the refrigerator and allow it to rest uncovered for 30 minutes. Meanwhile, preheat your oven to 350°F (175°C) and line baking sheets with parchment paper or silicone baking mats.

After chilling, the dough will be firm. Scoop out roughly 1.5 to 2 tablespoons of dough per cookie, roll into balls using your hands, and space them evenly on the prepared trays—approximately 8 cookies per sheet.

Bake in the preheated oven for 11 to 12 minutes. The centers should appear slightly underbaked and soft. For flatter cookies, tap the baking tray gently against the counter immediately after removing from the oven. Let cookies rest on the baking tray for 10 minutes, then transfer to a wire rack to cool.

While still warm, press additional chocolate chips into the tops and finish each cookie with a light sprinkle of flaky sea salt.