Small amount stock/water
Small amount of milk
Next chop up the celery, carrot, onion and garlic. Start off with the onion and garlic, frying them up in the same pot used to fry the meat [you'll be thankful for this when it comes time to do the dishes]. Once the onion gets soft follow up with the rest of the veggies.
Fry til the onion starts to turn brown, then dump the meat back in, along with the herbs or spice, fry a little more, around 5 mins. Next add the flour, tomato paste, and just a little stock first. It is much easier to add more liquid than to take excess liquid away, so always start by adding just a little, then top up. What we are trying to achieve here is a thick gravy that just coats the filling, so that the pie will be nice and moist, but not so much that it turns into a soup. So stir up the mixture and add stock as needed. Taste and season as needed.
Next, the potato crust. Peel potatoes and boil til a knife/fork pierce and slid out of it easily. Drain and let stand a few minutes in the mashing bowl for the steam to evaporate. Dump in margarine and a little milk and mash, adding more milk as needed. Mash according to your preference, either smooth or lumpy. For me, since it's going into a crust, I didn't bother too much with it and left it lumpy. Taste and season.
Once the meat filling is covered, use a fork to score as much ridges as possible across the surface of the crust. Again, this is to encourage crisping, as more surface is exposed to the heat when the potato crust is scored.Pop into the oven and bake til you are satisfied with the colour of the crust, roughly 30 mins. All the ingredients are cooked already, so the only purpose here is to crisp and brown the crust and warm up the pie a little. Here's my finished product =P