Heat the oil and butter in a large saucepan or flameproof casserole dish over a medium heat, and fry the onion, celery and a large pinch of salt for 10 mins until the veg is soft and starting to caramelise. Stir in the ginger and garlic and cook for 1 min more. Add the cumin, ground coriander, turmeric and curry powder. Fry for 1 min more. Stir in the swede and stock. Bring to a simmer. Cover and simmer for 1 hr 15 mins more until the swede is soft. Season. Blitz using a hand blender until smooth. Stir in the cream.

For the toasties, mix the cheddar with the spring onions, nigella seeds and coriander. Butter one side of each bread slice. Divide the cheese mix between two slices on the unbuttered side, add the chutney, and sandwich with the other slices, butter-side-out. Heat a medium pan over a medium-low heat, add the sandwiches, and weigh them down with another pan. Fry on each side for 4 mins until golden and the cheese has melted. Cut in half. Serve the soup in bowls topped with some yogurt and chilli flakes, with the cheese on toast on the side.