Cottage pie can be a sorry affair: grey, wet mince under watery mash, neither with much flavour. Or it can be sublime: rich, dark mince with creamy mash and a crusty, cheesy top. It’s all in the frying, so follow the instructions below and never mind if the cooker top ends up a mess.

1. Heat a tablespoon of oil in a heavy-based frying pan. If the mince is in a lump, flatten it on a plate. If it is in a supermarket pack, keep it flat. Press the slab of mince into the really hot pan using a fish slice and leave it there, without fiddling with it, for two minutes or more, then sneak a look to see if it's really brown. Flip it over and repeat. When both sides are brown, break it up to brown all the meat. Lift out with a slotted spoon and drop into a saucepan. Cook the black pudding as you have the mince, then remove with a slotted spoon and add to the saucepan.

2. Deglaze the frying pan by adding a splash of water and loosening the stuck-on bits with the fish slice. Tip on to the cooked meat. Turn down the heat under the pan and, using more oil as needed, fry the bacon, onion, celery and garlic until just turning brown. Stir in the tomatoes and bring to the boil, still stirring, then pour into the pan with the meat and black pudding. Add the tomato purée and thyme, and season. Simmer gently for 45 minutes, or until the sauce is thick and syrupy.

3. If the sauce is too thick, add a little water; if too runny, simmer until it is thick and barely liquid, stirring now and then to stop it sticking. Season well, then spoon into a pie dish deep enough for the mixture to reach 2-3cm (1in) from the top. Smooth the top, then allow to cool a bit and form a skin.

4. Heat the oven to 180 degrees/fan 160 degrees/gas mark 4 and start on the mash. Boil the potatoes and the sweet potatoes in separate saucepans of lightly salted water for 15-25 minutes until tender enough to mash.

5. Drain well and return to the pans. Add one or two thick slices of butter to each and mash well with a hand masher or stick blender, until light and smooth. Combine the two purées and season with salt and pepper.

6. Top the mince with spoonfuls of the mash, starting around the edges, until covered. Gently press down with the back of a fork. Mix the cheese and crumbs together and sprinkle on top of the pie. Bake for 25 minutes if the meat and mash are still hot, 45-50 minutes if they are cold.