Chop off and discard any woody bits from the broccoli stem, then roughly chop the whole head into pieces, blitz to a mince in a food processor and scrape into a large bowl.
Next, make the zhoug. Put the fresh coriander, parsley, chillies, cumin, ground coriander, cardamom, lemon juice, five tablespoons of oil and half a teaspoon of salt into the food processor and blitz to a smooth paste.
In a large nonstick frying pan, heat the remaining two tablespoons of oil over a medium heat and, when hot, add the blitzed broccoli and a half-teaspoon of salt. Cook, stirring every now and then, for about 10 minutes, until sweet and soft, then turn off the heat.
Cook the spaghetti in salted boiling water until al dente and, while it’s cooking, carefully dip a mug into the pot and collect a mugful of the hot pasta water.
Drain the pasta, tip into the broccoli pan, add the zhoug and toss to combine. Add some of the reserved pasta cooking water to loosen it – I used about eight tablespoons – until it looks nice and saucy. Check for seasoning, adjusting the salt, chilli or lemon as you wish, then serve on plates or bowls and eat hot.