Lightly grease a microwave-safe mug with cooking spray.
In a small bowl, combine the vanilla protein powder, baking powder, and coconut flour.
Add the maple syrup, egg, milk, and vanilla extract.
Stir until a smooth batter forms and no dry ingredients remain.
Pour the batter into the prepared mug.
If desired, sprinkle chocolate chips on top.
Microwave for 60 seconds, or until the Vanilla Mug Cake is cooked through in the center.
Allow the cake to cool for 1–2 minutes before serving.