In a large bowl, combine the cubed chicken, yoghurt, ginger, garlic, garam masala, coriander, cumin, salt and turmeric. Stir to combine and then cover and refrigerate for at least 1 hour.
Add 1 tablespoon of vegetable oil to a large frypan. Cook the chicken over a high heat until it is just cooked through. Take care not to overcook the chicken at this point as it will continue to cook in the sauce. Remove the chicken from the pan and set aside.
In the same pan, add the remaining 2 tablespoons of oil and heat over a medium-high heat. Add the tomato paste and cook for 2-3 minutes, until it has darkened slightly in color.
Add the passata sauce, cream, butter and sugar. Stir over heat until everything is combined. Add the chicken and fenugreek leaves and simmer for 5 minutes.
Serve over rice topped with chopped coriander and naan bread on the side.