In a bowl mix together the yoghurt, cumin, chilli, turmeric, ginger, mixed spice and salt, then stir in the chicken thighs. Cover and place in the fridge for at least 30 minutes.
Heat a little oil in a pan over a medium heat, and add the marinated chicken, chopped onion and garlic. Ensure the meat is sealed (approximately 2 minutes), then transfer everything to the slow cooker.
Sprinkle the cornflour, ground almonds and desiccated coconut over the mixture in the slow cooker. Add the tomato puree, mango chutney and 2 tablespoons of sultanas.
Dissolve the chicken stock in the hot water and add to the slow cooker, along with the coconut milk. Stir well, ensuring the sauce is completely combined, then cook on high for 3 hours or 6 hours on low.
Serve the curry sprinkled with the remaining sultanas and chopped almonds.
Spices - The quality of your curry will be determined by the spices. Fresh spices will taste much more fragrant than spices that have been sat in your cupboard for years!
Chicken - Don't chop up the chicken thighs too small - they'll shrink as they're cooked. Cutting a thigh into 2-3 pieces is usually about right.