In a small bowl, whisk together the flour, powdered sugar, cocoa powder, baking soda, and salt until well combined.
Pour in the milk and melted butter. Stir until a smooth, thick cookie dough forms. (No need to overmix—we aren't making bread!)
Add in the chocolate chips.
Shape the dough into a smooth ball. Press a few extra chocolate chips on top.
Microwave on high for 1 minute. (Times may vary slightly—it should look barely set in the center.)
Leave the cookie in the microwave for 5 minutes to finish cooking and set up. Trust me, patience here makes all the difference.
Enjoy! Dig into your ridiculously fast, warm, and yummy cookie.