600gpotatoes(fairly small - a floury variety like maris piper is ideal)
2tbsprapeseed or sunflower oil
400gtin lentilsgreen or brown
Bring a large saucepan of water to the boil. Clean the potatoes (no need to peel) and slice them thinly. Put them into the water to par-boil for 4-5 minutes, then drain and set aside.
Meanwhile, in a large frying pan or casserole, heat the oil and fry the sausages until they are browned. Remove from the pan, slice into bite-sized chunks and return to the pan.
Peel and slice the onion and add to the pan. Peel and trim the carrots and slice, then add to the pan. Cook for 3-4 minutes.
Clean the mushrooms, cut them in half and add to the pan along with the crushed garlic cloves and the leaves stripped from the sprigs of thyme. Cook over a medium heat until the mushrooms have released their juices and the pan is fairly dry.
Preheat your oven to 190°C (fan) / 375°F / Gas Mark 5.
Drain and rinse the lentils and add to the pan, then stir through the plain flour and cook for a minute or two, ensuring there are no lumps of flour.
Add the vegetable stock, soy sauce and tomato purée and season well with salt and black pepper. Bring to the boil then reduce to a simmer and cook for 8-10 minutes until the sauce has thickened and looks rich and glossy. If the sauce becomes too thick, just stir through a little more water.
Tip the filling into an ovenproof dish, then arrange the potato slices on top. Start by using up any broken slices first so they will be hidden, then starting from the middle overlap each potato slice just slightly until they completely cover the dish. You should have enough for two layers - the first one doesn't need to be neat, just the top layer!
Brush the potato slices with a little oil and sprinkle with salt and black pepper. Bake for 45 minutes or until the potatoes are crispy, golden and cooked through.
Don't over-boil the potatoes They should be under-cooked when you drain them, as they will continue cooking in the oven. If you cook them for too long they will crumble when you try to arrange them on top of the hotpot, (though will still taste good, don't worry!).Make sure the filling isn't too dry It will thicken even more as it cooks in the oven, so if in doubt, add a little more water to make plenty of sauce before pouring it into the dish, (see photos above for reference).If the potatoes are browning too quickly but not yet cooked through just cover the dish with foil for the remaining cooking time.