1. Put the dry ingredients in the mug and mix them together.
2. In a separate bowl, mix together egg replacer, then add it to the dry ingredients. Pour in the milk and mix it well. Add the oil and stir it up.
3. Add chocolate chips, vanilla and butter flavor and give it one last really good stir.
4. Put the mug in the microwave and cook it on high for 3 minutes. Stick a toothpick in the center, as far down as you can. If it comes out clean, it's ready to eat, if not, give it another 30 to 60 seconds.
You can eat it in the mug with a fork or spoon, or it's pretty easy to flip the mug upside down over a plate and give it a couple good smacks on the bottom and sides to get the cake to come loose.
Sometimes I pour a little raspberry sauce on mine (if I have some in the fridge), but if you have some leftover glaze or frosting from another treat you can spread it on the top of your cake and enjoy!
Source of recipe: I made cakes in custard dishes for a long time as a kid, usually on days when it wasn't nice enough to play outside. I was given a non-vegan recipe recently that was essentially the same thing, but in a mug instead, and cooking it in the microwave instead of the oven. I decided to use the mug and microwave idea with my vegan "rainy day" cakes.