Simmer the parsnips in salted water until tender - about fifteen to twenty minutes.
While they are cooking, fry the onions in the butter over a moderate heat until soft and translucent.
Stir in the spices and continue cooking for a further two minutes, until fragrant.
Drain the parsnips. Mash them with a potato masher, stirring in the butter, salt and freshly ground black pepper, then the sliced onions. Set aside.
In a large pan, cook the chopped leeks (or onions) and the diced carrot with the dripping or butter, until they are meltingly soft and golden - don't worry if they have caught slightly at the edges.
Add the sliced mushrooms and cook for a further five minutes, then stir in the minced meat. The meat must brown a little here and there, so do not stir it too often. Leave to cook for five minutes or so, breaking it up as necessary.
Add the flour and the tomato purée. Continue to cook, stirring regularly, for three or four minutes - tomato purée is bitter if not thoroughly cooked.
Pour on the hot stock, add a bay leaf and a sprig of thyme and bring to the boil.
Turn down the heat and leave to simmer very gently for 25-30 minutes.
Preheat the oven to 190C/375F/Gas 5.
Season the filling with salt, Worcestershire sauce and a few grinds of black pepper - be generous.
Scoop the mixture into a large baking dish and spoon dollops of mashed parsnip over the top. Bake for about 25 minutes until the topping is golden brown.
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