For ➏ 1kg pumpkin, such as kabocha
400 g sweet potatoes, unpeeled
15 cl olive oil
5 g sage leaves
1 red chilli, thinly sliced on an angle (10 g)
1 leek, trimmed & cut into 2mm rounds (200 g)
1 large onion, peeled & roughly chopped (240 g)
10 g piece fresh ginger, peeled & julienned
fine sea salt
½ ts smoked paprika
½ ts ground coriander
2 small potatoes (200 g)
60 g walnuts
1½ tbs maple syrup
10 g coriander leaves, finely chopped
10 g parsley leaves, finely chopped
1 ts finely grated lemon zest
Heat the oven to 220C (200C fan)/425F/gas 7. Put the whole pumpkin and sweet potatoes on a baking tray lined with greaseproof paper and roast, turning once halfway, for an hour, until soft and golden. Remove and turn down the oven to 180C (160C fan)/350F/gas 4. Once they’re cool enough to handle, use a metal spoon to peel off the pumpkin and sweet potato skins, and to scoop out the pumpkin seeds.
Meanwhile, put 80ml olive oil in a small saucepan on a medium heat, then add the sage leaves and fry for about two minutes, until deeply green. Use a slotted spoon to lift out the sage, transfer to a sheet of kitchen paper and leave to crisp up. Add the chilli to the hot oil, fry, stirring occasionally, for about two minutes, until deeply red, then transfer to the kitchen paper alongside the sage.
Transfer the hot oil to a large saucepan on a medium heat, add the leek, onion, ginger and three teaspoons of salt, and cook, stirring occasionally, for five minutes, until soft and translucent. Add the smoked paprika and ground coriander, cook for a minute, until fragrant, then add the cooked pumpkin and sweet potato flesh, and 1.6 litres of water.
Peel and grate the potatoes on to a chopping board, then add to the soup before they discolour. Bring the soup to a boil, then turn down the heat and simmer for 15 minutes.
While the soup is cooking, make the nut brittle. Line a small baking tray with greaseproof paper, top with the walnuts, maple syrup and a quarter-teaspoon of salt, and toss to coat. Roast, stirring once halfway, for about 10 minutes, until toasted and golden brown, then remove, sprinkle the fried sage and chilli on top, toss to combine and leave to cool. Once the nut mix is cool, scrunch up the paper to crush the brittle into smaller pieces.
Make the herb oil by combining the coriander, parsley, lemon zest, remaining 70ml oil and a quarter-teaspoon of salt in a small bowl.
Once the soup has cooked, take off the heat and blitz with a stick or regular blender until smooth and velvety. Add a splash more water to loosen, if need be, then divide between six bowls. Scatter the maple walnut brittle on top and serve drizzled with the herb oil.
