Add your chopped chocolate and butter to a microwave-safe bowl. Microwave in short 20-second bursts, stirring between each one, until everything turns smooth and glossy. This usually takes about two minutes total, so don't rush it or you risk burning the chocolate.
In a separate large bowl, beat the eggs, granulated sugar, and brown sugar together with your mixer. Keep beating for a few full minutes until the mixture turns pale and frothy. This step is what gives the cookies their signature crackly, shiny top later on.
Pour the melted chocolate mixture and vanilla extract into the egg mixture. Beat everything together until it's fully combined and glossy. At this point the batter should look rich, thick, and almost like brownie batter waiting to be baked.
Sprinkle in the flour, cocoa powder, salt, and baking powder. Use a spatula to gently fold everything together until just combined. Try not to overmix here, since overworking the batter can make the cookies tougher instead of fudgy.
Stir in the chocolate chips until they're evenly distributed throughout the thick batter. Make sure no dry flour pockets remain hiding at the bottom of the bowl. This is also when I taste-test a tiny bit of batter, purely for quality control.
Cover the bowl and refrigerate the batter for a full 30 minutes. Skipping this step causes the cookies to spread too thin and bake unevenly. It feels like a long wait, but it's the secret to that perfect thick, fudgy shape.
Preheat your oven to 350°F and line two baking sheets with parchment paper. Scoop the chilled dough into rounded balls, spacing them about 3 inches apart so they have room to spread properly. Bake for 8 to 10 minutes, until the tops look shiny and cracked, then let them cool completely on the pan.