Begin by preheating your oven to 180°C (350°F) and lining your baking sheets with parchment paper.
Melt the unsalted butter in a small saucepan over low heat until just liquid, then let it cool slightly so it doesn’t cook the egg later.
In a large mixing bowl, whisk together the brown sugar and granulated sugar until combined and slightly fluffy, then pour in the cooled melted butter and stir until smooth.
Add the large egg and vanilla extract to the sugar mixture and whisk until the mixture looks glossy and well combined, about 30 seconds.
Sift the cocoa powder, baking powder, and salt into the wet ingredients to prevent lumps, then gently fold everything together with your spatula until smooth and thick.
Stir in the semi-sweet chocolate chips evenly throughout the dough, making sure they’re well distributed.
Using a cookie scoop or spoon, portion out dollops of dough onto your prepared baking sheets, spacing them about 2 inches apart as they will spread slightly during baking.
Bake the cookies for 10-12 minutes until the edges are set and slightly crisp, but the centers still look soft and fudgy.
Once baked, remove the cookies from the oven and let them cool on the baking sheet for about 5 minutes to firm up.
Transfer the cookies to a wire rack to cool completely, or enjoy them warm for that gooey, chocolatey experience.
Finish by sprinkling a tiny pinch of sea salt on top if desired, then serve and enjoy these decadent brownie cookies.
