You could probably use a bunch of green onions if you don't have leeks. But obviously leeks make everything better.
And it doesn't get much easier than this.
Black carrot and leek soup
Makes 6 servings
2 Tablespoons extra virgin olive oil
1 large leek
2 medium black (or any) carrots, chopped into small pieces*
1 teaspoon Marmite
6 cups boiling water
2 medium potatoes, diced*
1 teaspoon dried thyme leaves
1/2 teaspoon dried sage
3/4 teaspoon salt
1/4 teaspoon ground black pepper
In a large pot, heat the olive oil over medium-high heat. Add the leeks and carrots and sauté until they are starting to brown and smell a little toasty. Dissolve the Marmite in the boiling water. Pour into the pot, then add potatoes and seasonings. Bring to a boil and simmer gently with the lid on for 15-20 minutes or until the potatoes are cooked. Serve hot.
* For added nutrition, leave the skins on. You won't even taste the carrot peels in the finished product and the potatoes are cut small enough that the skins are super manageable. If you're going to eat your potato and carrot skins, though, it is best to use organic ones--otherwise the skins may have absorbed a lot of pesticides and such from the ground.