Add all ingredients except chocolate chips to a 10-12 ounce microwave-safe mug.
Stir with a fork or mini whisk.
Microwave on high until the cake is cooked, about 1 minute 45 seconds. Pause cooking halfway through by opening up microwave to prevent cake from overflowing.
If desired, sprinkle chocolate chips on top.
Serve warm and ENJOY!
Notes
Add a pinch of instant espresso powder for deeper chocolate flavor.