Preparation

• 1
  Cut the cauliflower into small florets. Peel the sweet potato and chop into fine dice. Peel and finely chop the onion. Peel and grate the ginger and peel the garlic.
• 2
  Put the cumin seeds, mustard seeds, ground coriander, turmeric and chilli into a pestle and mortar and grind together.
• 3
  Heat the sunflower oil in a large saucepan and gently sauté the onion for 3 minutes. Add the ginger and crushed garlic, stir in the spice mixture and cook gently, stirring, for a minute or two.
• 4
  Add the sweet potato, stir well and cook for a further 2-3 minutes, stirring to prevent it from sticking.
• 5
  Add the cauliflower florets, gradually add and stir in a litre of hot vegetable stock and bring to a simmer. Cook for about 20 minutes, or until the vegetables are really soft.
• 6
  Blend the soup until it is smooth and thick. Stir in 3 heaped tablespoons of thick Greek yoghurt and heat through for a few minutes, adding a little more vegetable stock if the soup is too thick. Season well with salt and black pepper.
• 7
  Garnish each bowlful of soup with a spoonful of Greek yoghurt and a little black pepper, accompanied by wedges of warm naan bread.