Preheat your oven to 200°C/400°F/gas 6. Place the squash, cumin and crumbled chilli on to a baking tray. Drizzle with olive oil, mix together and place in the preheated oven. Roast for 45 minutes until the squash is cooked through.
Once the squash is roasted, heat a large saucepan and pour in a splash of oil. Add the celery, garlic, parsley stalks and two-thirds of the onion, and cook gently with a lid on until softened. Drop in the roasted squash and let it sweat for a few minutes, then pour in the stock. Bring to the boil, turn down the heat and simmer for 15 minutes. Add the chickpeas and simmer for 15 minutes more.
Meanwhile, toast the reserved squash seeds with the almond flakes, fennel, sesame and poppy seeds in a little olive oil until they are nicely coloured all over.
Season the soup well and, using a hand-held blender, whiz for a few seconds so it thickens, but there are still some chunky bits. Keep warm while you mix together the lemon zest, chopped parsley leaves and mint leaves. Chop the remaining onion until it’s really fine, then mix into the zesty mixture.
To serve, spoon half a teaspoon of harissa paste into each bowl. Divide the zesty herb mixture between the bowls and ladle over the soup. Stir each bowl once with a spoon, then sprinkle with the toasted seeds and almonds and finish with a drizzle of extra virgin olive oil.