Heat the oil in a large pan then add the onion and carrots and sweat them gently over a low heat for 20–30 minutes, being careful that they don’t catch. They should be no more than lightly browned. This is the most important stage as it is when the vegetables release most of their flavour.
Add the potato, season with salt and pepper and cook for another 3 minutes, stirring frequently. Cover the ingredients with water and simmer until the potato is fully cooked, about 15–20 minutes. Finally, add the chopped coriander and whizz with a hand blender until the soup is really smooth.
• a dollop of crème fraîche or cream
• toasted almonds
• toasted and lightly crushed cumin seeds
• a couple of drops of orange flower water
• walnut, hazelnut or sesame oil
• 1 heaped teaspoon of ground mixed Moroccan spices, such as caraway and cumin with a little hot chilli
• chopped parsley or chervil