Bring the water to boil in a large pot. Put in the shanks and simmer for 1 to 2 hours. The liquid should have reduced by at least a quarter.
Transfer the shanks to a large ovenproof dish and add tomatoes, balsamic vinegar, wine, garlic, rosemary, salt and pepper and 1 litres of the liquid the shanks were cooked in. Cover with aluminium foil and cook in the oven for 14 hours at 120degC.
Remove from oven, strip the meat from the bones and remove bones. Transfer the mixture to a saucepan, bring to a simmer and add the cornflour to thicken to the desired consistency (you may like to add extra cornflour).
The filling can be used to make either individual pies or a family-sized one. Spray small ramekins or a large pie dish with cooking spray and line with pastry. Fill with the meat mixture and cover with a pastry lid. Brush with egg wash and cook for 15 minutes at 200degC or until golden.
Serve with pumpkin and kumara mash topped with a tomato and rosemary sauce.
