Peel, halve and roughly chop the onion. Finely slice the chilli, then peel and finely slice the ginger and garlic. Pick the coriander leaves, finely chopping the stalks. Halve, deseed and roughly chop the peppers. Click off and discard the green leaves from the cauliflower, then break the cauliflower into florets and roughly chop the stem. Quarter the fresh tomatoes. Carefully halve the butternut squash, then scoop out the seeds with a spoon and discard. Slice into 2.5cm wedges, leaving the peel on but removing any thick skin, then roughly chop into smaller pieces. Drain the chickpeas. Heat 2 tablespoons of oil and the butter in a large casserole pan on a medium-high heat, add the onions, chilli, ginger, garlic and coriander stalks and cook for 10 minutes, or until softened and golden. Add the peppers, butternut squash, chickpeas and jalfrezi curry paste, then stir well to coat. Add the cauliflower, the fresh and tinned tomatoes, breaking the plum tomatoes up with the back of a spoon. Add the vinegar and 1 tin's worth of water, and stir again. Bring to the boil, then turn the heat down and simmer for 45 minutes with the lid on. Check the curry after 30 minutes and, if it still looks too liquidy, remove the lid for the rest of the cooking time. When the veg is tender, taste and season to perfection with sea salt, black pepper, and a squeeze of lemon juice. Delicious served with poppadoms or fluffy rice and with a few dollops of natural yoghurt, a sprinkle of coriander leaves and a few lemon wedges for squeezing over.