Soak the chana dal overnight or atleast 5-6 hours. Next day drain it and grind with green chilly, ginger, garlic and salt to a coarse mixture without adding water.
Transfer to a bowl and make small lemon sized balls. Set aside.
In a thick bottomed pan or kadai, add yogurt and water. Whisk well and make to a thin buttermilk consistency. Add sugar, salt and mix well.
Then add besan and whisk well until there are no lumps. Now heat this over low-medium flame, stirring occasionally.
Once steam starts coming out, add the grated ginger. Increase the heat to medium-high and allow the kadhi to boil, stirring in between.
Once the kadhi starts bubbling and rising up, gently add the chana dal balls one by one. Let the balls cook for 10-12 minutes. Do not stir or disturb the balls.
Once the balls are cooked they will start coming up. Remove from heat.
To prepare kadhi tempering, heat ghee in a small pan and add mustard seeds. When it crackles, add green chilly and curry leaves. Then add turmeric powder, red chilly powder, coriander powder and hing. Pour into the kadhi.
To prepare the tempering for balls, heat oil in a small pan and add mustard seeds. When it crackles, add cumin seeds and green chilly. Then add turmeric powder, red chilly powder and coriander powder and hing. Set aside.
When serving, take the chana dal balls in a plate. Break them and pour the second tempering over the balls.