Steps
In a microwave-safe mug, combine the flour, sugar, cocoa powder, baking powder, and salt. Mix well.
Add the milk, vegetable oil, and vanilla extract to the dry ingredients. Stir until smooth.
Fold in the chocolate chips if using.
Microwave on high for 60-90 seconds, or until the cake has risen and is set in the center. Keep an eye on it to prevent overflow.
Let it cool for a couple of minutes before enjoying straight from the mug.