4 tablespoons flour
4 tablespoons sugar
2 tablespoons unsweetened cocoa powder
pinch of salt
2 tablespoons vegetable oil
3 tablespoons milk
1 egg
Splash of vanilla or other flavoring, cinnamon or peppermint

In a medium sized mug (be sure it is microwave safe), add the vegetable oil, egg, milk and whatever flavoring you are using. Mix up these ingredients until well combined.
Add the flour, sugar, cocoa powder and salt. Again mix until well combined. If you are using any of the suggested add ins, now's the time to add them.
Cook in the microwave on high for about 2 1/2 minutes depending on your brand of microwave. The end result should look like the photo at the top.
This recipe is very flexible! You can use cake or all-purpose flour (or even self-rising flour), other flavorings instead of vanilla, water instead of milk, change baking time to get the amount of moistness you prepare. You can add the dry ingredients before the web if you prefer. Others have substitute pudding mix for the cocoa powder for pancake mix for the flour.