In a food processor, blend the spinach to a purée using one or two tablespoons of water to loosen the mixture. Set aside.
Heat the vegetable oil in a pan over a medium heat. Add the cardamom pods, bay leaves and cinnamon and fry for 20-30 seconds.
Add the green chillies and onion and continue to fry for 4-5 minutes, or until caramelised.
Meanwhile, blend the ginger, garlic and tomatoes to a smooth paste in the food processor.
When the onions have caramelised, add the paste, chicken pieces and remaining spices to the pan and stir well to combine. Season, to taste, with salt and simmer for 12-15 minutes, stirring regularly.
Add the yoghurt, stir well and continue to simmer the mixture until the sauce has thickened and almost dried out.
Stir in the spinach purée and continue to simmer for 10-12 minutes, or until the chicken has cooked through. Season, to taste, with salt and freshly ground black pepper, then serve with rice.