Chop the chicken into bite size chunks. Chop the yellow onion. Add the chicken and onion to the slow cooker.
In a small bowl combine 2 teaspoons cumin, 1 teaspoon cinnamon, 1 teaspoon cayenne pepper, 1 teaspoon garam masala, 1 teaspoon black pepper, and 1 teaspoon kosher salt.
Sprinkle the spices over the chicken and use your hands to coat the chicken well. Sprinkle 1 and ½ tablespoons butter chunks over the chicken. Add ginger to pot
Put the lid on and cook on high for 2-3 hours, or on low for about 5 hours.
When the chicken is cooked, remove the lid and add the tomato sauce and cream (turn the crock pot up to high at this point if it's not already.)
Replace the lid and let cook on high for another 20-30 minutes or until thickened and bubbly on the edges.
Taste it and stir in some plain yogurt. The amount is up to you. This makes it a little more creamy and also tempers the heat. Sometimes I don't add any, if I'm feeding kids I add more.
Stir in the fresh cilantro.
Serve with hot rice and naan.
