Remove all fat traces and connective tissue from the chicken breasts, dice them into medium sized chunks, them add them to a large bowl. Add the remaining marinade ingredients and mix thoroughly. Taste the marinade sauce and check if you need more salt or boost up any of the spices (it's totally up to you). Wrap in cling foil and insert it in the fridge for at least 4 hours.
Heat up a large frying pan on high heat. Add the marinated chicken chunks a single layer and cook on both sides until slightly brown. Take out the cooked meat (it won't be cooked all the way through) and set aside. Repeat the process with the remaining meat.Total cooking time here will depend on how large your pan is, your stove and how large the meat chunks are. but this process took me about 15 minutes and 3 batches to cool all the meat.
In the meantime, boil the rice together with the spices, then completely drain. Season with salt if needed.
Take a deep large frying pan and heat up on medium heat. Spray the olive oil and add the butter to melt.Add the chopped onions and minced garlic cloves. Stir for 1-2 minutes, then add all sauce spices and seasoning. Stir for half a minute to release the spiciness and then add the tomato passata and the tomato juice.Stir, cover with a lid and set to simmer for 10 minutes. Add the hot water, stir and set to simmer for another 10 minutes on low heat.(Optional) Take away from the heat and puree the sauce with an immersion blender.Add the chicken chunks and the cream and leave to simmer on medium to low heat for 15 minutes with the lid on. Take the lid away and check to see if the largest chicken chunk is cooked through. If it is, then you are all set, if not, leave to simmer until completely cooked, but be careful not to overcook it.
Add the rice and chicken tikka masala to a deep serving plate, then garnish with freshly chopped parsley and enjoy!