Preheat your oven to 180°C (350°F). Line a baking sheet with parchment paper or a silicone mat to prevent sticking. Gather all your tools and ingredients for easy access.
Melt the butter in a small saucepan over low heat, listening for a gentle bubbling sound. Once melted, remove from heat and stir in the dark chocolate chunks until smooth and shiny. Let this mixture cool slightly; it should feel warm but not hot.
In a large mixing bowl, whisk together the brown sugar, eggs, and vanilla extract until the mixture is smooth, slightly thickened, and fragrant—this takes about a minute. The eggs should be fully incorporated and the sugar starting to dissolve.
Pour the slightly cooled chocolate-butter mixture into the egg mixture, stirring gently until combined and glossy. The batter should look rich and smooth with a velvety texture.
Sift together the flour, cocoa powder, and baking powder into a separate bowl. Gradually fold these dry ingredients into the wet mixture using a spatula, doing so gently to keep the batter thick and fudgy. Stop mixing as soon as there are no streaks of flour remaining.
Gently fold in an additional handful of dark chocolate chunks to ensure gooey pockets of chocolate throughout the cookies. The batter should be thick, almost like brownie dough, and scoopable but stiff.
Using a cookie scoop or tablespoon, portion out the dough onto the prepared baking sheet, spacing each about 2 inches apart. Slightly flatten each mound with the back of a spoon for even baking and a prettier top.
Bake in the preheated oven for 12-15 minutes. The edges should be golden and slightly crisp, while the centers remain shiny and fudgy. The cookies may crack on top—this natural fissure is perfect and indicates they are baked just right.
Remove the baking sheet from the oven and let the cookies rest for about 5 minutes. Then, transfer them carefully to a wire rack to cool completely. As they cool, they will set into a perfect balance of crispy edges and chewy centers.
Finish by sprinkling a tiny pinch of sea salt on top of the warm cookies for extra flavor contrast, if you like. Serve these cookies warm or at room temperature for maximum fudgy goodness and crunchy edges.
