Prep: 1. Slice and rinse leeks (we like to use the whole leek but you can use just the white and light green part if you prefer). 2. Cut sweet potatoes into pieces (peel if desired). 3. De-rib and chop kale. Make: 1. Heat the oil in a large saucepan over medium heat. 2. Add the leeks and cook, stirring occasionally, until they begin to soften, 3 to 4 minutes. 3. Add the tomatoes and simmer for 5 minutes. 4. Add 6 cups water and bring to a boil. Stir in the sweet potatoes, kale, lentils, thyme, season with salt and pepper to taste. 5. Simmer until the lentils are tender, 25 to 30 minutes. 6. Serve hot.
Leeks can be particularly dirty, make sure to rinse them thoroughly - https://www.youtube.com/watch?v=SdX6W6qpoEk