Mix the flour, sugar, and baking powder in a small bowl.
Stir in the milk and vanilla extract, then stir in the melted butter.
Mix in the fresh blueberries.
Spray a mug with non-stick spray.
Pour in the mug muffin batter; adding a few extra blueberries to the top if you like (I like).
Microwave for 90 seconds then check to see if it's done.
If not, add 15 seconds at a time until cooked through.
Top with more blueberries (you can never have too many blueberries!) and enjoy!!