Heat a large saucepan and dry-fry the cumin seeds and chilli flakes for 1 min, or until they start to jump around the pan and release their aromas
Scoop out about half of the seeds with a spoon and set aside
Add the oil, carrot, lentils, stock and milk to the pan and bring to the boil
Simmer for 15 mins until the lentils have swollen and softened
Whizz the soup with a stick blender or in a food processor until smooth (or leave it chunky if you prefer)
Season to taste and finish with a dollop of yogurt and a sprinkling of the reserved toasted spices
Serve with bread of your choice