Soak the channa overnight in plenty of water. Before pressure cooking, change the water a couple of times. Pressure cook for 3 whistles.
When the pressure falls down, add ginger, potato, cumin, turmeric powder, chili powder and green chilies, and mint. Pressure cook for another 2 whistles or till tender.
In a non-stick pan, melt the ghee, fry the onions, green chilies until they are lightly browned. Stir them into chickpeas with salt and garam masala powder.
Remove the pan from the heat and stir in the lemon juice and fresh mint.