In a bowl mix butter milk,mango puree,salt,besan and turmeric powder beat well without lumps and keep ready.
Keep a kadai add ghee and when hot add mustard seeds,cumin,and then asafoetida.
When mustard seeds splutter add curry leaves and red chillies then ginger green chilli mixture and saute for some time.
Then add the buttermilk mixture to it and let it boil for some time,add jaggery to it.
When all the rawness goes and when thick switch off.
Can serve with roti's and hot rice.
Notes
you can omit mustard when tempering by adding cumin alone.
over ripe mangoes does a good job for this kadhi/curry.
Even redchillies can be omitted its optional.
If you don't have buttermilk can dilute the curd and use.