In a pressure cooker cook the chickpeas with 600ml of water, salt and teabag, cook it for 4 whistles or 20 minutes.
Switch off the heat and let the steam escape by itself and then realise the pressure valve before opening the pressure cooker.
When chickpeas are cooking in pressure cooker, you can make a tadka for adding to the chickpeas.
Heat a frying pan, add 1 tbsp of peanut oil to the pan, add onion paste along with bay leaf and black cardamom. Fry the paste till it is light brown in color.
Add rest of the spice powders and fry them with onion paste for 1/2 minute on slow heat.
Add tomatoes and tamarind paste and cook everything together for about 6-7 minutes on medium heat, continue stirring in between to prevent the masala from burning.
Cook the masala till it starts to leave the sides of the pan and then switch off the heat and transfer the tadka to the pressure cooker in which chickpeas were cooked.
Mix everything together and add cubed potatoes to it.
Put the pressure cooker lid back on and pressure cook the chana aloo for 10 minutes.
Open the lid and in the side take another small tadka pan heat the ghee and immediately add green chilli, switch off the heat and probably cover this pan otherwise sometimes green chilli upon heating tends to split.
Pour this ghee chilli mixture after opening the lid of pressure cooker.
Serve hot with whole wheat kulcha or steamed Basmati rice.