Cut the chicken thighs into 1-inch pieces. Place the chicken in the slow cooker.
Peel and mince the ginger and dice the onion. Drain the can of diced tomatoes. Place the ginger, onion, and tomatoes in the slow cooker.
Next add the garlic, brown sugar, kosher salt, coriander, garam masala, cinnamon, and cumin to the slow cooker. Stir until they are well combined. Cook on high for 3-4 hours or on low for 6-8 hours.
When cooking is complete, stir in the coconut milk and heavy cream until they are well blended. Heat the tikka masala for an additional 30 minutes on high. Serve and enjoy!
Place your chicken tikka masala over a bed of rice and garnish with freshly chopped cilantro.