Make the banana cream: Combine the heavy cream (or milk), banana, sugar, and vanilla extract in the jar of a personal blender. Blend until smooth. If necessary, stop blending and shake or stir the jar to mix; continue to blend until fluffy.

Fill a large glass with ice; add the chilled coffee. Pour the banana cream over the iced coffee. Garnish with a pinch of cinnamon.

The banana cream can be made ahead of time but will need to be blended again before serving.