Butter chicken with onion sultana pilaf

Ingredients

• 1 tablespoon garam masala
• 1 teaspoon chilli powder
• 2 clove garlic, chopped coarsely
• 4 centimetre piece fresh ginger (20g), grated
• 2 tablespoon lemon juice
• 1/3 cup (90g) tomato paste
• 1 cup (150g) roasted, unsalted cashews
• 1/4 cup (60ml) buttermilk
• 800 gram thigh fillets, chopped coarsely
• 40 gram butter
• 1 brown onion (200g), sliced thinly
• 1 cinnamon stick
• 6 cardamom pods, bruised
• 425 gram can crushed tomatoes
• 3/4 cup (180ml) chicken stock
• 1/4 cup (60ml) buttermilk, extra
• 1/4 cup loosely packed fresh coriander leaves
• 2 brown onions (300g), sliced thinly
• 2 teaspoon yellow mustard seeds
• 1 1/2 cup (300g) basmati rice
• 3 cup (750ml) chicken stock
• 1/3 cup (55g) sultanas