Steam cook the banana and mash it with a fork.
Add grated coconut and cardamom powder.
Add melted jaggery.
Add wheat flour, salt and baking soda.
Knead to make a smooth dough. If the dough is too sticky, you can add little more wheat flour.
To make vadas, dip your fingers in water. Take a small portion of this dough, make a ball, slightly flatten the ball with your thumb, next make a hole in the center.
Heat oil in a pan and fry it.
Fry both sides on medium flame till both sides are turned into golden brown in color.
Serve hot with a cup of hot tea.