Mash the ripe banana in a microwave-safe mug until smooth.
Add the granulated sugar.
Add vegetable oil, vanilla extract, and ground cinnamon, then mix until well combined.
Add the all-purpose flour, baking powder, and salt, then mix until a smooth batter forms.
Add the chocolate chips and mix evenly into the batter.
Place a few banana slices and a small piece of chocolate in the center of the batter.
Microwave on high for 60–90 seconds, or until the cake is set.
Allow the mug cake to cool slightly, Serve warm and enjoy.