Put the wet masala ingredients (chopped onions, ginger, and garlic) in a blender with a few tablespoons of water and blend to a smooth paste.
Cooking
Heat the oil in a deep pan and add the sliced onions. Fry until caramelized.
Add the wet ground masala you prepared earlier and fry for 4-5 minutes on high heat.
Add the chicken and dry ground spices (coriander, turmeric, red chilli, and garam masala). Mix well and fry on high heat for 5 minutes. Add ½ cup water and cover the pan. Turn down the heat to medium and cook for 10 minutes.
Add tomato paste and yogurt cook uncovered for 15 minutes.
Drain the can of chickpeas, rinse, and add to the chicken. Cook for 5-6 minutes or until the chickpeas are coated with the masala (curry).
Add slit green chillies and kasuri methi (dried fenugreek). Give the chicken a stir and switch off the heat. Cover the pan again and allow it to rest for 5-10 minutes. Serve hot with naan or pita bread.
Notes
Kasuri methi or dried fenugreek is easily available in any Indian or Pakistani grocery or the international aisle of a big supermarket.
Don't add a lot of water as the sauce will become too thin. You want a thick sauce for this recipe.