Peel the bananas and cut them into medium sized pieces.
Blend it to a fine paste.
Heat a heavy bottomed kadai (pan), and transfer this banana puree into it. Add jaggery and stir.
Keep stirring until the sugar and jaggery melt, and the mixture starts to darken.
Now add lemon juice, and keep stirring until the mixture starts to become glossy.
Keep adding one tablespoon ghee at a time, and stir until it melts into the mixture. Keep repeating this step of adding ghee and stirring until the mixture starts to thicken, and stick around the edges and white frothy surfaces develop. This will take about 4-5 tablespoons of ghee and 15-20 minutes.
Finally, add cardamom powder, stir well. Serve hot or chilled with dry fruits of your choice. You can also roast the dry fruits in ghee before adding it to the halwa.