In a mixing bowl combine the chicken marinade: 1 cup full-fat canned coconut milk, 1/2 tsp ground cinnamon, 1/2 tsp paprika, 1 tsp garam masala, and 1/2 tsp sea salt. Add the chopped chicken (2 to 3 pounds) and stir until all pieces are coated. Cover and refrigerate at least 15 minutes (ideally 1 to 8 hours).
While the chicken is marinating, make the tikka masala sauce. In a medium saucepan over medium heat melt 3 Tbsp ghee.
Add 1/2 yellow onion, finely chopped, to the melted ghee and sauté 5 to 8 minutes, until the onion is translucent.
Add 5 cloves garlic (minced), 1 Tbsp fresh ginger (peeled and grated), 2 tsp garam masala, 2 tsp ground cumin, 1/2 tsp ground cardamom, 1/4 tsp ground turmeric, and 1 1/2 tsp sea salt. Sauté 1 to 2 minutes, stirring, until the spices are fragrant.
Add the remaining sauce liquids and flavorings: 1 1/2 cups full-fat canned coconut milk, the 128-ounce can crushed tomatoes, and 2 Tbsp tomato paste. If using, add 1 Tbsp pure maple syrup. Bring the mixture to a gentle boil, then reduce heat and simmer for at least 15 minutes (longer if you want deeper flavor).
Use an immersion blender to blend the sauce until smooth and creamy. If using a regular blender, cool slightly and blend in batches, then return the blended sauce to the saucepan and keep warm.
Turn your Instant Pot to the Sauté function and let it heat for a couple of minutes. Add the marinated chicken with all of the marinade and sauté 3 to 4 minutes, stirring, until the outside of the chicken just starts to brown.
Pour the blended tikka masala sauce over the browned chicken in the Instant Pot and stir to combine.
Secure the Instant Pot lid, set the valve to Sealing, select the Pressure Cook (Manual) function, change the pressure setting to Low, and set the cook time to 35 minutes.
When the cook cycle finishes, allow the Instant Pot to enter Keep Warm for an additional 20 to 30 minutes (this continues a gentle, natural pressure release). After that time, carefully move the valve to Venting to release any remaining steam.
Open the lid, stir the Chicken Tikka Masala to combine, and serve hot with your choice of rice or cauliflower rice.