Combine marinade ingredients with lamb and mix well. Cover and chill for at least one hour.
Soak cashews in boiling water for 10 minutes, then blitz together in the blender until smooth.
Heat oil in a large pot and fry onion until soft. Add curry spices and cook for one minute until fragrant.
Add marinated lamb, cashew paste and stock. Bring to a simmer, cover and cook on low for at least 1 hour and until lamb is tender and sauce is reduced.
Season with salt and pepper to taste and serve with yogurt naan, fresh coriander and raita.
