1-2 Tbsp. cocoa powder (depending on how chocolatey you want your cake)
1 standard-sized mug
In mug, crack egg, add powdered sugar and cocoa powder. Whisk together with a small whisk until well mixed. Microwave for 50-60 seconds, until the cake is cooked through (but not overcooked!) Top immediately with a handful of milk chocolate chips, hot fudge, whipped cream, or ice cream.