You can use a selection of squashes for this, or just a single variety. Check how tough the skins are before preparing them as some squashes taste delicious cooked with the skin on. If your specimens have tough skins, then buy a bit extra to compensate for losing some of the flesh.
1kg squash, peeled if necessary, seeds removed and cut into 2-3cm chunks
Salt and freshly ground black pepper
60g ghee or vegetable oil
3 medium onions, peeled, halved and roughly chopped
5 large cloves of garlic, peeled and crushed
1tbsp chopped root ginger
3 small, medium-strength chillies, sliced
1tsp cumin seeds
tsp fenugreek seeds
tsp onion or Nigella seeds
1tsp cumin powder
1tsp freshly grated turmeric or 1tsp turmeric powder
1 pinch saffron strands
A good pinch of curry leaves
1tsp fennel seeds
1tsp mustard seeds
2tsp tomato purée
Half a lemon
1.3litre vegetable stock (a good cube will do)
3tbsp chopped coriander leaves
Season the pieces of squash. Heat half of the ghee in a large, heavy-bottomed pan and fry the squash on a high heat until lightly coloured. Remove with a slotted spoon and put to one side. Add the rest of the ghee to the pan and fry the onions, garlic, ginger and chilli for a few minutes until they begin to soften. Add all of the rest of the spices and continue cooking for a couple of minutes with a lid on to release the flavours, stirring every so often.
Add the tomato purée, lemon and stock, bring to the boil, season with salt and pepper and simmer gently for 45 minutes. Take a cupful of the sauce from the pan and blend in a liquidiser until smooth and pour it back into the sauce. Add the pieces of squash and simmer for about 15 minutes or until tender, then add the coriander and simmer for a further 5 minutes, seasoning with salt and pepper if necessary. Scatter over the chopped coriander, and serve with basmati rice.