Heat a large saucepan over a medium heat.
Add a little olive oil and sauté the leek, ginger and garlic for 4-5 minutes or until softened.
Add the fennel seeds, turmeric, cumin and coriander and sauté for 2-3 minutes until fragrant.
Add the carrots and stock and simmer for 15 minutes or until the carrots are soft.
Remove from the heat and blend the mixture with a hand blender until smooth.
Return the soup to the heat, add the lentils and simmer for 25-30 minutes or until the lentils are soft.
Season well and serve.