Spray a frying pan with low calorie cooking spray, and fry the onion, ginger and chilli until brown.
Place the rogan josh curry paste in a sterilised jar. The mix will last a few days. You can also freeze it into ice cube trays.
Place the lamb into a non reactive bowl along with 2 tbsp of the curry paste. Add 2 tbsp of fat free yogurt (natural or Greek) and some salt and pepper.
Fry off 4 tbsp of the rogan josh curry paste for a few minutes until it begins to stick to the bottom of the pan