Wash and soak black chana overnight. Drain and pressure cook with 1 cup of water, salt and turmeric. Simmer for 10 minutes after first whistle. Switch off and once pressure is released, open and evaporate water if any. Keep aside.
Pressure cook sweet potato with 1/2 cup of water for 1 whistle. Switch off. Once pressure is released, open peel the potato. Roughly chop into 1 inch cubes. Mash lightly. Keep aside.
Prepare green chutney. Wash and drain the leaves thoroughly. Grind the leaves together with rest of the ingredients listed. Keep aside.
Whisk yogurt with sugar.
Mix the spices in a small bowl and keep aside.
In a big bowl, mix cooked black chana, mashed sweet potato, chopped onions and green chilli. Add green chutney and spice mix. Toss well. Add dates, fig and lime juice to taste.
Add few tbsp of whisked yogurt to the serving bowl. Top it with black gram and potato mix. Serve immediately.
Green chutney - Can be prepared ahead and stored in the refrigerator for upto a week.