1 Heat the oil in a large saucepan. Add the onion and carrots and cook over a medium heat for 5 minutes until soft.
2 Add the minced beef and cook for 3 minutes until brown. Add the Worcestershire sauce, stock and tomato purée.
3 Cover and simmer for 30 minutes. Season to taste with salt and pepper.
4 Preheat the oven to 190°C (170° fan) 375°F gas 5. Grease 4 individual baking dishes.
5 Put the sweet potatoes in a large saucepan and cover with cold water. Bring to a boil and cook for about 15 minutes, until tender. Drain and mash with the butter and season to taste with nutmeg, salt and pepper.
6 Spoon the meat into the dishes. Top with the mashed sweet potatoes and bake for about 30 minutes until the potatoes are lightly browned and the filling is piping hot.