Butter Chicken

Butter Chicken is a staple in any indian restaraunt in Vancouver and this is the best I have done in attempting to replicate it. This is really really good. Honestly.
Prep:20m Cook:45m Servings:4

Ingredients
1C raw cashews
2t garam masala
2t ground coriander
3/4t chili powder
3 cloves garlic chopped coarsely
2t fresh ginger, grated
2T white vinegar
1/3C tomato paste
1/2C yogourt
1kg chicken thighs or breast cut into 1" chunks
2T butter
1 onion, finely chopped
1 cinnamon stick
4 cardamom pods, bruised
1t paprika
1 small can crushed tomatoes (400g)
3/4C chicken stock
1C whipping cream
rice and naan to serve it with

Directions
1-.Stir nuts, garam masala, coriander, and chili in a small lightly heated frying pan. Toss until nuts are lightly browned.
2-.Put nut mixture in food processor, add garlic, ginger, vinegar, paste and yogourt. Process until smooth.
3-.Put chicken into mixture and mix thoroughly. Allow chicken to marinate for at least a few hours or overnight in the refrigerator.
4-.Melt butter in a large saucepan, cook onion with cinnamon and cardamom until browned. Add paprika, crushed tomatoes and stock. Bring to a boil, reduce heat and simmer uncovered for 45 minutes.
5-.Remove cinnamon and cardamom (if you can find it). Stir in cream and simmer for another 5 minutes. Serve over basmati rice with naan.