Cut the chicken into large chunks and place into a slow cooker.
Spray a medium non-stick pan with oil spray and place over medium heat. Once hot, sauté the onion, garlic, ginger and salt for about 3 to 5 minutes, or until softened. Add the garam masala, curry powder, red pepper flakes and tomato paste and sauté for another 3 to 5 minutes.
Add to the chicken in the slow cooker along with the crushed tomatoes. Stir everything to evenly combine, and set slow cooker on high for 4 hours.
After 3½ hours, stir in the coconut milk and cook for the remaining 30 minutes uncovered so the sauce can reduce slightly. Add cilantro for garnish just before serving.
Nutrition information is calculated using a leading industry software. That being said, brands can vary, and there may be slight fluctuations in the numbers.