Stir together the dry ingredients in a 6 to 8-ounce microwave-safe mug.
In a separate bowl, use a fork or small whisk to thoroughly beat one egg. Measure out 1 tablespoon of the beaten egg and add it into the mug.
Add the vanilla, milk, vegetable oil to the mug and stir to make a batter. Mix in ½ of the chocolate chunks and sprinkle the other half over the top.
Microwave 1 minute to 1 minute 15 seconds. The mug cake is done when it no longer appears wet across the top of the mug cake.
