Spiced sweet potato and leek soup with stilton

1. Cut a 4cm length from the white part of one leek and set aside. Roughly slice the rest. Heat the butter and 1 tbsp oil in a large pan, add the spices and roughly sliced leeks and fry for about 10 minutes, until softened. Add the garlic and cook for 1 minute more. Add the stock and sweet potato, season and bring to a simmer. Cook for 10-15 minutes or until the potatoes are tender.

2. Meanwhile, make some frizzled leeks to garnish. Heat the remaining 1 tbsp oil in a frying pan over a medium-high heat. Halve the reserved leek, then finely slice lengthways into matchsticks. Add to the hot oil, and move constantly with tongs until golden and crisp. Remove from the pan and drain on kitchen paper. Sprinkle with sea salt and set aside.

3. Remove the soup from the heat and cool slightly. Transfer to a blender and whizz until smooth (in batches if needed). Return to the pan and reheat gently; check the seasoning and add lemon juice to taste. To serve, divide between 4 warm bowls, crumble over the blue cheese and top with the frizzled leeks.