Cut the chicken into medium-size pieces and place in a bowl. Add the chilli powder, lemon juice, yogurt, half of the ginger and 1 teaspoon of the garam masala, and mix well. Cover and put in the fridge to marinate for at least 1 hour, or overnight.
Preheat the grill to high. Thread the chicken onto skewers (if using wooden ones, soak in water for 30 minutes before cooking).
Put the skewers on a baking tray and grill for 5 minutes on each side, until cooked through and no pink colour remains. When done, remove the meat from the skewers.
Heat the oil in a large pan and fry the onions over a medium heat for 10 minutes, until golden. Stir in the garlic and remaining ginger, and cook for 1 minute. Stir in the paprika and remaining garam masala, and fry for about 1 minute, until fragrant.
Meanwhile, cook the rice according to pack instructions.
Pour the tomatoes and stock into the onion pan, and bring to the boil. Turn down the heat and simmer for 5 minutes, until slightly thickened. Stir in the cream and add the chicken pieces. Simmer for 1 minute, then stir through half the coriander.
Serve the chicken curry with the rice, and garnish with the remaining coriander. Great served with warm naan bread.