Heat olive oil in a large saucepan and brown the mince; set it aside.
In the same saucepan, add some more olive oil and then add the onion, carrots, celery and
garlic; cook until vegetables have softened a little (10-15 minutes).
Add the flour and tomato purée, and cook for 1-2 minutes.
Return the beef to the saucepan, then add the wine if you are using it; if required, allow it to
reduce a little.
Add the beef stock, Worcestershire sauce, thyme and bay leaves and allow to cook at a simmer,
uncovered, for 45 minutes.
Check after 30 minutes to ensure the gravy has thickened; if not, increase the heat a little for
the last 15 minutes.
Season and then remove the bay leaves (and thyme if not dried).
While the mince is cooking, boil potatoes until soft, drain the water and steam-dry the potatoes
for a few minutes.
Mash the potatoes and add the milk, butter, cheese and nutmeg; don't forget to season to taste.
Spoon the meat into an ovenproof dish, then cover with the mash and sprinkle cheese on top (if
desired).
If it's being eaten immediately, place the dish in the oven (200°C) for 30 minutes, or until the
top is golden brown.