Mix grated coconut,sugar and cardamom powder until it becomes soft and keep it aside
Add hot water into rice flour and make chapathi like dough(not too watery)
Add some salt to taste
Spread some oil on banana leaf pieces and place a small amount of dough in the center of the leaf and flatten it
Fill the coconut-sugar mixture and fill some thumbappovu above it
Fold the leaf in half and press the sides
Place the ada in a steamer and cook for 10-20 minutes
Tasty Thumbapoo ada is ready to serve