Slow Cooker Butter Chicken

I haven't tried this recipe yet, but am eager to give it a chance!

Stir-fry on medium heat until chicken has color and onions are translucent:
4-6 boneless chicken thighs, cubed
1 onion, diced
3 cloves garlic, minced
2 T butter
2 T oil

Transfer to crockpot and add:
15 green cardamom pods held in cheesecloth (um... could I just add some ground cardamom??)
2 tsp curry powder
1 T curry paste (mild for me!!)
1 tsp cayenne powder (optional)
2 tsp tandoori masala
1 tsp garam masala
1 can coconut milk
1 cup plain yogurt
1 can tomato paste
Salt to taste

Mix gently and cook on high heat 4-6 hours or low heat 6-8 hours
Serve with basmati rice and warm naan bread.