In a small microwave-safe glass container, mash the ripe banana thoroughly with a fork until smooth.
Crack in the egg and mix it into the mashed banana.
Add cocoa powder, baking powder, and a pinch of salt.
Mix vigorously with a fork until the batter is uniform and mostly lump-free.
Stir in the chocolate chips.
Microwave on high for 90 seconds to 2 minutes, until cooked through but still moist in the center.
Let the brownie cool slightly, transfer to a plate, cut into four pieces, and serve warm.
