In a big mixing bowl, take semolina, rice flour, refined flour and a cup of water. Whisk to dissolve the lumps completely.Finely chop green coriander in a bowl.Also, finely chop green chilly and ginger in separate bowls.To the preared batter add 1.5 more cups of water and whisk well. The consistency of batter for making rava dosa needs to be thin.Now add green chilly, ginger, green coriander, salt, asafoetida and crushed black peppercorns to the prepared batter and mix well.Cover the prepared rava dosa batter and keep aside for 15 minutes. Dosa batter is ready.Preheat a non stick tawa or pan for roasting the dosas and evenly spread some oil over it.Then pour 2-3 tsp batter on the tawa and spread in circular motion. Keep it layer thin. Increase the flame to maximum and roast until it gets golden brown in color from bottom. Keep the flame medium-high.When the dosa turns golden brown in color from beneath, take it off flame and stack on a plate or casserole.To make another dosa, clean the pan after it cools down then pour the batter in circular motion and cook till it gets golden brown and crisp. Similarly fry the rest as well until the whole batter is utilized.Serve these delicious and crispy rava dosas steaming hot with side assortment of any Indian dip/chutney like green coriander chutney, coconut chutney, kasundi, peanut chutney. In fact they taste super with piping hot sambhar as well.