In a frypan add some olive oil and the onions. Sautee until soft. Add the mushrooms and garlic, cook for a further two minutes.
Add the mincemeat and breakdown until cooked. Add in the water in order to deglaze the pan.
Next add the Vegemite, Worcestershire sauce, tomato sauce, stock powder, chef it up spice mix, salt and pepper. Allow to cook for five minutes. Dissolve your cornflour in some water and add this along with the gravy powder to the mincemeat mix and cook for 2 to 3 minutes until it thickens.
Allow this mixture to cool prior to adding it to the shortcrust pastry . Then top with puff pastry and cook in the pie maker.