Remove any wilted or brown leaves from the cauliflower. Cut the cauliflower and broccoli into bite-size florets, then finely chop the stalks and remaining leaves. Heat the oil in a large, deep saucepan over a medium heat and cook all the stalks and leaves, the onion, celery, carrot and garlic, partially covered with a lid, for 10 mins until everything is slightly softened. Remove the lid and stir in the spices and stock. Bring to a simmer, cook for 5 mins, then stir in the cauliflower and broccoli florets. Continue cooking, covered, for 10 mins more until everything is tender. Remove from the heat and blitz using a hand blender until thick and creamy. Season to taste.

Meanwhile, for the crumble, heat the oil in a small pan over a medium heat and toast the breadcrumbs, seeds and chilli flakes for 4-5 mins until golden and fragrant. Remove from the heat, season and stir in the cheese. Sprinkle the crumble over the soup to serve.