First in a bowl add sattu,besan,rava,salt and buttermilk and mix well and keep aside it for 15 mins.
When it is dry, switch of gas and keep aside it.
In other side, heat oil in pan add cumin seeds, when crackle, add onion in it, when translucent,add garlic, green chilli,hing powder in it and saute,now add bathua and methi leaves in it and keep on medium to high flame, add salt and mix well.
When it is dry, switch off gas and keep aside it.
Now take sattu better add bathua and methi mixture and add termeric, fennel, chilli powder and chopped coriander in it and mix well.
Adjust salt and water in it and prepare a dosa like better of it.
Now heat dosa pan,pour and rub some oil,pour the mixture and drizzle some oil over it, when one side done, flip it and cook other side.
Make all chilla's like this from remaining better,now serve chilla hot with pickle