I like to marinate the chicken for 48 hours. You could get away with an hour or two but the longer you marinate the chicken the better.
Most restaurants use tandoori style chicken for chicken tikka masala. Here is my recipe
800g Tandoori chicken tikka (A link to my recipe is above)
2 tablespoons ghee or vegetable oil
4 tablespoons garlic and ginger paste
1 tablespoon cumin
1 teaspoon turmeric
1 tablespoon coriander powder
1 tablespoon dried fenugreek leaves
2 tablespoons garam masala
1 tablespoon paprika
1 tablespoon sugar (more or less to taste)
2 tablespoons tomato paste
700ml heated base curry sauce (Links to my recipe above)
250ml double cream
1 tablespoon red food colouring powder (optional)
2 tablespoons butter
1 small bunch fresh chopped coriander
Salt and pepper to taste
Juice of one lemon
Heat the ghee/oil in a large pan or wok over medium high heat
When bubbling hot, add the cumin, turmeric, coriander powder and garam masala.
Stir the spices around in the hot oil for about 30 seconds and then add the tomato paste and garlic and ginger paste.
Continue stirring all the ingredients for another 30 seconds and then add the heated curry sauce.
Bring to a simmer and add your chicken tikka.
Simmer for about a minute and pour in the cream and red dye if using.
Add the butter and stir until it melts into the sauce.
Stir in the fresh coriander, season with salt and pepper and finish with a squeeze or two of lemon.