Mix Dry Ingredients. In a microwave-safe mug, whisk together the flour, sugar, baking powder, and salt.
Add Wet Ingredients. Stir in the milk, vegetable oil, and vanilla extract until smooth.
Add Chocolate Chips. Fold in the chocolate chips, ensuring they are evenly distributed.
Microwave. Microwave on high for 1 to 2 minutes, or until the cake has risen and is set in the center. The exact time will depend on your microwave's power.
Serve. Allow the cake to cool for a minute before digging in. Enjoy your warm, gooey chocolate chip mug cake!