Separate and peel the garlic cloves, then peel and roughly chop the onion. Pick the coriander leaves (reserve for later) and roughly chop the stalks.
Put the coriander stalks, garlic and onion in a blender with the rest of the paste ingredients and whiz until smooth, then scrape the paste out into a bowl.
Roughly chop the tomatoes and put in the blender, season well with sea salt and freshly ground black pepper, then blitz until smooth and put aside for later.
Remove and discard the cauliflower leaves, break off the florets and slice the stalk. Peel and roughly slice the onions.
Toss the cauliflower and red onions into a large casserole-type pan, with half the curry paste. Add 600ml of water and roast in the hot oven for 40 minutes, stirring halfway through.
Meanwhile, cut the chicken into finger-sized strips, toss them in the bowl with the remaining curry paste, cover and pop into the fridge.
After 40 minutes, carefully move the hot pan from the oven to the hob. Drain and add the chickpeas, along with the stock and blitzed tomatoes, and simmer on a medium heat for about 30 minutes, or until the consistency you like.
Meanwhile, preheat a large griddle pan over a high heat. Thread the chicken pieces on to 6 or 8 metal or wooden skewers. Drizzle with a little oil, season from a height, and cook on the screaming hot griddle for around 10 to 12 minutes, turning each one every now and again, until gnarly, sizzly and cooked through. Squeeze over some lemon juice and give the pan a good shake, scraping the bottom of the pan for around 30 seconds to get all the intense flavour. Transfer everything to a plate and set aside.
Go back to your curry and mash a few times to thicken up the sauce. Add the delicate veggies (peas, beans, corn and spinach) for the last 3 minutes of cooking, then have a taste and correct the seasoning.
Deseed and finely chop the chilli, if using, leaving in the seeds for extra heat.
Marble a few dollops of yoghurt, if using, through the sauce, scatter over the reserved coriander leaves and the chilli, then take straight to the table. Serve with fluffy rice, the chicken skewers and anything else you fancy.