Spray a frying pan with low calorie cooking spray and add the gammon and chicken. Gently saute the meat until it has coloured. Pour in the water, stock cube, mustard powder and 1tsp of garlic granules then add the leek and mushrooms.
Make a well in the centre of the mixture and add the quark. Very gently stir working from the centre out until fully combined. It may sound odd, but this will prevent the quark from splitting! Season with salt and pepper to taste.
Drain the potato cubes and arrange onto the top of the dish. Spray with low calorie cooking spray and sprinkle 1 tsp of garlic granules over the top.