In a mixer- grinder add bananas, sugar and grind well so that it becomes like a paste.

Now add room temperatured milk into paste and again grind well.
After that, chop chocolate finely for decoration.

Pour banana milk shake into serving glasses and keep inside fridge for 10 mins along with chopped chocolate.

Finally, after 10 mins, take your banana milk shake out and decorate with chopped chocolate, as shown in picture.