Cut the chicken breasts into bite-sized pieces and transfer them to a slow cooker.
Sauté the onions and garlic in a little ghee (or olive oil) over medium-high heat in a skillet until softened, then stir in the ginger, tomato paste, and spices. Add in the diced tomatoes with their juices. Transfer to the crock pot with the chicken lightly toss together.
Cover the crock pot and cook for 3-4 hours on high or 6 hours on low. Ten minutes before serving, stir in the coconut milk. *If you want a thicker consistency, use arrowroot powder or flour (add 2 Tbsp. to 1/4 cup cold water); stir well and add to the mixture. Taste and add more spices or salt, if needed.
Serve over farro or rice with fresh cilantro sprinkled over the top of each serving.