Start by adding the butter to a microwavable mug.
Then add the salt, cocoa, vanilla and sugar and mix well.
I used a fork to mix.
Finally, put the flour in and mix well- but don't over mix otherwise it won't be moist- it will be stiff.
Microwave for 1 minute (depending upon how powerful your microwave is).
I actually did it for 45 seconds.
A way to check its cooked is insert a cocktail skewer through the centre, and if it comes out clean, then it's done!
When it's cooked, let it cool and enjoy! (I burnt my tongue because I couldn't resist!) It comes out lovely and moist and you could top it with whipped cream.