Roast a green chili on open flame until the skin starts to wrinkle and brown spots appear.
In a mortar and pestle add roasted green chili, garlic cloves, cumin seeds and coarsely pound them.
Add the pounded chili garlic mixture and salt to taste in to the buttermilk or whisked curd(if you're using curd/yogurt) and give it a good mix.Note : If using Curd add water to dilute the consistency. For 1 cup of curd add 2 cups of water.
Tempering
In a small wok/kadhai prepare the tempering. Place this wok on slow flame, add freshly churned butter or oil.
Coarsely pound some garlic cloves and cumin seeds.
Now add mustard seeds, coarsely pounded garlic cumin seeds and curry leaves. And roast until garlic turns golden brown.
Now add torn red chilies, slit green chillies and pinch of turmeric powder and fry for a minute.
Add the tempering to the churned buttermilk and add chopped cilantro.
Serve chilled salla charu with rice and chappati pappu(boiled plain toor dal).
Notes
You can omit roasting the green chili on open flame and just add it in tempering.
If you're using fresh curd/yogurt add the clotted cream(malai) or sour cream to add a nice tang to the salla charu.