For the spice mix Combine all spice mix ingredients together in a small mixing bowl.
For the dish:Place the cubed chicken in a medium-size mixing bowl. Tip: Chicken is easier to cut into cubes when it is semi-frozen. Sprinkle half of the spice mixture on the chicken and toss to coat.
Refrigerate chicken for at least 30 minutes and up to 2 hours to let the flavors macerate.Heat ½ tablespoon of the oil in a medium-size skillet over medium-high heat.
Add the chicken and cook until chicken is browned, about 2 minutes per side. Remove chicken, place on a plate and set aside In same skillet, heat the remaining oil over medium heat.
Add onion and cook for about 5 minutes and then stir in ginger and garlic. Cook for another 2 minutes, continuously stirring to prevent burning.Add in the remaining spice mix and stir to combine.
Add in the tomatoes and coconut milk and decrease heat and simmer on low for about 10 minutes. Tip: For deeper flavors, keep at a very low simmer for an hour or turn heat off and cover pan.
Add in the chicken, and cook for about 3 minutes, then reduce heat to low and cover pan. Tip: For a smooth sauce, run the tikka masala sauce in the blender for about 1 minute.