Peel the onions. Cut one into wedges and the rest into a reasonably fine dice.
2 large onions
Fry the onion wedges in a little oil or ghee until soft and starting to go golden around the edges. Remove from the pan and set aside.
2 tbsp ghee or oil
Add some more oil or ghee to the pan and fry the diced onions gently until they are golden. This takes at least 5 minutes, if not longer.
Once the onions are turning golden, add the spices and cook a little longer until fragrant.
1 tbsp medium curry powder, 1½ tsp ground cumin, 1 tsp ground coriander, 1 tsp paprika, 2 tsp garam masala, ½ tsp chilli powder
Add the tomatoes to the onions, together with half the stock and the onion and ginger paste. Stir, scraping all the onion from the bottom of the pan into the sauce.
½ can chopped tomatoes, 200 ml chicken stock, 1 tbsp ginger and garlic paste
Tip into a bowl or jug so that the sauce is deep enough to submerge the blender and blitz to a smooth sauce. If you have made a double batch of sauce to freeze, separate what you want to store now.
Return the blended sauce to the pan and add the chopped chicken, chopped green chillies and the lightly crushed cardamon pods.
2 green chillies, 400-450 g chicken thighs, 4 pods cardamon
Stir well. If you are using ready cooked chicken, you may want to add a little more stock. Raw chicken will release some juices into the sauce, and will not need it.
Cover the pan and bring to a simmer. Cook on the stove top on the lowest heat for about 25 minutes until the chicken is cooked through. Check half way though cooking and add more liquid if needed.
Return the fried onion wedges to the curry and stir through, ensuring that they are hot before serving.