In a microwave-safe mug, combine the flour, sugar, cocoa powder, baking powder, and salt. Mix well until all the dry ingredients are evenly distributed.
Add the milk, vegetable oil, and vanilla extract to the dry ingredients. Stir until just combined and no dry flour remains.
Carefully fold in the chocolate chips, ensuring they're evenly dispersed throughout the batter.
Microwave the mug on high for 40-60 seconds. The exact time will depend on your microwave's power; you want the cake to be set around the edges but still slightly gooey in the center. Keep an eye on it to avoid overflowing!
Let the mug cake cool for about a minute before serving; this helps the lava center develop more.
Notes
Serve with ice cream or whipped cream for extra indulgence.