Mix all spices; seal in snack-size bag labeled “Tikka Masala Spice.”
Toss ccubed chicken with 2 tsp. vegetable oil and 1 tsp. of the spice mix.
Place chicken into a quart bag; flatten, seal, and label "Chicken for Tikka Masala."
Place onion, tomatoes, tomato paste, garlic, and chili pepper (if using) into a separate quart bag. Flatten, seal, and label "Veggies for Tikka Masala."
Put the bags of the spice mix, chicken, and veggies into a 1 gallon zip top freezer bag. Seal and label "Chicken Tikka Masala."