For Sauce: In a medium sized saucepan on a medium heat, warm your oil and gently fry the garlic, ginger and chili for 1-2 mins. Then go in with, the remaining 1 tsp of tikka powder, cumin and coriander powder. Add a splash of water to stop the spices from burning then add tomato puree and the rest of the water. Bring the mix to a simmer and drop chicken in to cook through. Cook for 10-15 mins. If the sauce starts to dry out add a little more water.