1. Break up any lumps in the meat with a fork.
2. Skin and slice the onions.
3. Melt the dripping in a saucepan, and fry the onions until softened but not coloured.
4. Stir in the flour, and cook gently for 1-2 minutes, stirring all the time.
5. Gradually add the stock, without letting lumps form, and stir until boiling.
6. Reduce the heat, and simmer for 2-3 minutes until the sauce thickens.
7. Stir in the mince, cover the pan, and simmer for 20 minutes.
8. Season well, replace the lid, and simmer for 10 minutes longer or until the mince is cooked through and tender.
9. Meanwhile, prepare the potatoes and boil them in salted water until tender.
10. Mash them until smooth with a seasoning of salt, pepper, nutmeg, enough milk to make them creamy, and butter, if liked.
11. Put the meat and sauce into a greased pie dish or shallow oven to table baking dish.
12. Cover with the potato, smooth the top, then flick it up into small peaks or score a pattern on the surface with a fork.
13. Bake for 10-15 minutes in a hot oven, 220°C, gas mark 7, until browned on top. Serve hot.