Rinse and soak chana overnight. Later drain them and rinse well. Pressure cook them with 1 cup water for 3 to 4 whistles until soft and tender. To cook in instant pot, pressure cook for 16 to 18 minutes and let the pressure release naturally.
Pour 1½ tablespoon oil to a pan and heat it. Saute ginger, garlic and green chilies for a minute.
Add onions and saute until golden and fully cooked. Then stir in spinach and cook for 2 to 3 minutes, just until wilted. Transfer to a plate and cool this completely.
Later transfer the cooled ingredients to a blender and add coriander leaves. You may want to set aside one of the green chilies, taste test and add it later. Make a fine or coarse paste as per your liking. We prefer smooth paste.
How to make chana saag
While the greens cool, heat another tbsp oil in the same pan. Add tomatoes and salt. Saute and cook until soft and mushy.
Add garam masala, cooked chana and 1½ cups liquid (chana cooked water plus more water).
Cover and simmer chana for 5 minutes. Then reduce the heat and transfer the saag paste to the pan.
Stir well and cook just for a minute or 2 until chana saag begins to bubble.
Taste test and adjust salt and more garam masala if required. Turn off the heat. Transfer chana saag to a serving bowl.
Tempering (optional, but recommended)
On a low heat, melt 1 tbsp butter or ghee in a small pan. Add dried red chilies and chopped garlic. Fry on a low heat until garlic turns slightly golden but not brown. Add hing and turn off.