In a large frying pan, heat the oil over medium-high heat. Add the chicken and all the marinade and cook for a few minutes, then turn the chicken pieces so they cook on the other side. Add the tomato sauce, sugar and salt and let simmer on low-heat for about 5-10 minutes, until the chicken is cooked completely through. Stir in the whipping cream. Whisk the cornstarch and water together in a small bowl or cup with a fork then pour into the sauce, while stirring the sauce. Let the sauce come to a simmer again and cook for a minute or two to thicken, then salt to taste and serve with basmati rice and naan bread.