Slow Cooker Butter Chicken

1 lb boneless chicken thighs cut into bite-sized pieces
1 onion, diced
3 cloves garlic, minced
2 tbsp butter
2 tbsp oil

15 green cardamom pods (strung together with a needle and thread or put in a cheesecloth.  Can also substitute 2 tsp ground cardamom)
2 tsp curry powder
1 tbsp curry paste (I like Patak’s mild curry paste)
1 tsp cayenne powder (optional. It’s really hot if you add this)
2 tsp tandoori masala
1 tsp garam masala
1 400 ml can coconut milk
1 cup plain yogurt
1 5.5 fl oz can of tomato paste
Salt to taste

In a large frying pan on medium high heat, add the oil and butter.  Stir fry chicken, onion and garlic until the chicken has some color and the onion is translucent. Then pour entire contents of pan into crock pot. Then add the rest of your ingredients.  Mix gently and cook on high heat 4-6 hours or low heat 6-8 hours.  Serve with basmati rice and warm naan bread.