Preheat the oven to 180 C / Gas 4. Add the cream, yoghurt and cornflour in a bowl and stir. Set aside.
Mix together the ginger, turmeric and curry powder. Sprinkle half of the spice mixture onto a piece of greaseproof paper. Place the chicken fillets on top. Cover the chicken in the rest of the spice, then top with another piece of greaseproof paper. Flatten the chicken with a rolling pin.
Add half the oil to a pan. Heat up.
Put the chicken in the pan to seal in the spice, turning once. Remove the chicken from the pan and put in casserole or ovenproof dish with a lid.
Add the rest of the oil to the pan with the onions and garlic. Then add the cream mixture. Add to the dish, over the chicken.
Place the dish in the oven for 45 to 50 minutes until the chicken is cooked.