Stir vanilla extract, milk and honey into the butter. Add flour and baking powder and stir until combined.
Microwave mug cake 1.5 minutes.
Video
Notes
Note on Cook Time: Every microwave varies and the one I have is not that strong so if you have a high-powered microwave check it at a minute and keep an eye on it. You want it to rise and the top to look damp but not wet.