Chicken Tikka Masala

how to prepare(cook)Chicken Tikka Masala?
Ingredients

Chicken - 500 gms boneless pieces
For Marinating
Ginger and garlic paste - 2 tsp
Turmeric powder - 1/4 tsp
Chilly powder - 1/2 tspn
Coriander powder - 1 tspn
Garam masala - 1 tspn
Cumin powder - 1/2 tspn
Salt
Curd - 1/2 cup beaten well
For the gravy

One onion chopped
Tomato puree 2 tspns
Turmeric powder- 1/4 tspn
Coriander powder 2 tspn
Chilly powder -1 1/2 tspn
Ginger and garlic paste - 1 tspn
Salt to taste
Oil 3 thsp
Garam masala powder - 1/2 tspn
Coriander leaves finely chopped for garnish
Cream 1 tspn optional for garnish
Method
Marinade for one hour. Then put this on skewers and grill till cooked. Or you can put it on a pan and let the flame be low or even bake it till done.
Heat oil in a vessel, fry onions and add ginger and garlic paste.
Let it fry well till the oil separates.
Then add all the powdered masala, and the tomato puree, salt to taste add a little water and let the gravy thicken.
Then add the chicken pieces and cook for a while, finally when the gravy is thick, remove from fire.
Garnish with coriander leaves and cream.