Measure out the flour and hot chocolate mix into the mug. Stir.
Crack the egg into the mug. Stir a bit after adding the egg so the cup doesn't overflow.
Add water and oil.
Stir until thoroughly moistened. Make sure to scrape the bottom of the mug with your spoon to avoid any leftover pockets of dry ingredients.
Put the mug in the microwave on high and set the timer for 3 minutes.
When done, it will settle back into the mug.
Not exactly healthy food, but you can improve it a bit by using olive oil in a mister instead of cooking spray, and make your own hot chocolate mix. You could also use a flour other than wheat.