Clean, wash and soak the sanwa millet in enough water for atleast 2 hours.
Drain and blend in a mixer to a fine paste using 2 tbsp of water.
Transfer the mixture to a bowl, add the rajgira flour, buttermilk, ginger-green chilli paste and rock salt and mix well. Cover and keep aside to ferment overnight.
Divide the batter into 8 equal portions and keep aside.
Heat a non-stick tava (griddle), pour a ladleful of the batter on the tava (griddle) and spread it in a circular motion to make a 125 mm. (5″) diameter thin dosa.
Smear a little oil along the sides, cook till both the sides of the dosa turns golden brown in colour and fold over to make a semi-circle.
Repeat with the remaining batter to make 7 more dosas.
Serve hot with green chutney or peanut curd chutney.