in a grinder or blender take 1 medium sized chopped onion, 2 medium sized chopped tomatoes, 1 inch chopped ginger, 4 to 5 garlic cloves and 1 chopped green chili.
grind to a fine paste.
no need to add water while making the paste as the juice of the tomatoes will help in making the paste.
keep the paste aside.
heat 2 to 3 tablespoons oil in a pan or kadai/wok.
add the whole garam masala (spices) - 1 teaspoon cumin seeds, 1 large tej patta, 2 inch cinnamon, 2 to 3 cloves, 2 green cardamom and 2 to 3 black peppercorns.
fry the whole garam masala mentioned above till the oil become fragrant. but don't burn them.
add the ground paste and saute till the oil starts to leave the sides of the masala paste.
keep stirring often. saute for 7 to 8 minutes or till the oil starts to leave the sides of the masala paste. stir while sauteing so that the paste does not stick to the pan.
next add all the dry spice powders - ½ teaspoon turmeric powder (haldi), ¼ teaspoon red chili powder, 1 teaspoon coriander powder (dhania powder), 1 pinch asafoetida (optional) and ½ or 1 teaspoon dry mango powder (amchur).
mix very well and saute for a minute. now add the cooked chole and stir.
add 1 to 1.5 cups water or add as required. also add salt as per taste and mix well.
simmer chana masala gravy on a low or medium flame for 12 to 15 minutes or till the curry thickens. don't cover the pan. stir occasionally.
mash a few chickpeas with the back of spoon. this helps in thickening the gravy.
lastly add 1 slit green chili and 1 teaspoon garam masala powder or chole masala powder. mix well and simmer for a minute or two.
check the seasoning and add more salt or spice powders if required. garnish chole masala with coriander leaves.
you can also garnish the chole with some slit green chilies and ginger julienne.
serve chole with onion slices, lemon wedges along with bhatura. enjoy the chole bhature.