Take 1 cup of roti dough and make 3 medium size dough balls from it.
Then roll 3 medium thick roti from the dough ball. Keep it aside.
Now in a mixing bowl, take 1.5 cups besan and add water gradually to make medium thick and spreading consistency of the batter.
Whisk the batter for 2 minutes so it will become light and fluffy.
Then add salt, turmeric powder, red chilli powder, cumin powder, black pepper powder, garam masala, dry mango powder, hing, ajwain, chopped onion, spicy green chilli and coriander leaves. Mix well. Batter is ready.
Now take a plate and grease it with oil.
Place one rolled roti on plate and spread an even layer of besan batter.
Now place 2 nd rolled roti on the batter and spread besan batter on it.
Then place 3 rd rolled roti on the batter and spread besan batter on it. (refer to video).
Now boil 2-3 cup of water in a vessel. Place a hole plate on it. now place nasta plate on it and steam it for 15 minutes on high flame.
Then cool down the steam nasta and cut it into square pieces.
Then in a pan, add oil, mustard seeds, sesame seeds, curry leaves and chopped green chilli. saute it.
Add nasta pieces and cook them on low-medium flame till they crisp from both sides.
Serve crispy nasta with chutney or tomato ketchup.