Preheat the oven to 400'F/200'C/gas mark 7.

Peel and quarter the potatoes, boil in water until tender for about 15-20 minutes.

While the potatoes are cooking, pour the oil into a large frying pan or wok.

Sauté onions in the oil until tender over a medium heat for 10 minutes. (If you are adding vegetables, put the carrots in with the onions, add the corn and/or peas either after cooking the onions or after the meat has been added and initially cooked).

Add the ground beef and sauté until brown. Add seasoning and Worchesteshire sauce. Add beef stock and cook, umcovered, over a low heat for 10 minutes, adding more stock a necesary to keep moist.

Mash potatoes with butter, season to taste.

Place beef and vegetables into a baking dish. Distibute mashed potatoes on top. Rough with a fork so there are peaks that will brown nicely. You can use the fork to make some designs in the potatoes as well.

Bake in the oven until bubbling and brown (for about 30 minutes).