Take a microwave safe mug.
Put all the ingredients (except water) in the mug in the given order- all-purpose flour, cocoa powder, baking powder, powdered sugar, oil and milk.
Mix the batter nicely, preferably with a butter knife or a fork as it goes easily into the bottom edges of the mug also.
Once everything gets mixed, sprinkle about 1/2 teaspoon water on the top. Do not mix after adding the water.
Keep the mug in the microwave for 1 minute, at 100% power. Do not use the convection mode.
Check for doneness of the cake by inserting a toothpick.
If done then take out or keep it for 10 or 20 seconds more.
Serve as it is or take out in a bowl. To invert it, run a butter knife around the baked cake.
