Later that day I made another one, this time in a breakfast bowl using double the recipe, and it also worked well, and there was enough for all of us to have a little serve with cream.
Put in the microwave on high - mine took just under 3 minutes, but this will vary between ovens. (I checked mine after 2 mins and decided it could do with a little bit longer.)
Not bad when you consider it took a bowl, a spoon, a few ingredients and 2 and a bit minutes in the microwave!
And really it's more of a pudding than a cake - you scoop some out and put it in a bowl rather than slicing it up.
Below are the ingredients for a small bowl; halve the amounts for a mug cake.
8 tbsp plain flour
8 tbsp granulated sugar
4 tbsp cocoa
6 tbsp full-cream milk
4 tbsp olive oil
splash of vanilla essence