Place the semi-sweet chocolate in a microwave-safe bowl and heat in 20–30 second intervals, stirring after each session, until fully melted and smooth. Set aside.

In a large mixing bowl, beat together the softened butter, brown sugar, and white sugar for about one minute until creamy. Incorporate the eggs and vanilla extract, blending until the mixture achieves a smooth and glossy consistency. Add in the melted chocolate and mix thoroughly.

Sift the flour, cocoa powder, espresso powder, baking powder, and salt directly into the wet ingredients. Mix on low speed until just combined to prevent any dry ingredient dispersion.

Gently fold in approximately 1/4 cup of the chocolate chips using a rubber spatula, ensuring an even distribution throughout the dough.

Refrigerate the dough uncovered for 30 minutes. While the dough chills, preheat the oven to 350°F and line baking sheets with parchment paper or silicone mats.

Once chilled, the dough will firm up. Scoop 1.5 to 2 tablespoons of dough per cookie, roll into balls, and arrange on prepared baking sheets, spacing adequately—typically eight per sheet.

Bake for 11–12 minutes, allowing the centers to remain slightly underdone for that classic fudgy texture. For flatter cookies, gently tap the sheets on the counter immediately upon removing from the oven.

Allow cookies to cool on the baking sheet for 10 minutes before transferring to a wire rack. While still warm, press the remaining chocolate chips onto the tops and sprinkle lightly with flaky sea salt.

Serve warm or store in an airtight container at room temperature for up to 3 days.