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.
Mix until a smooth batter forms with no visible lumps.
Pour the batter into the prepared mug.
Sprinkle chocolate chips on top if desired.
Microwave the Vanilla Mug Cake for about 60 seconds or until the center is just set.
Allow it to cool for 1–2 minutes before enjoying.