In a large pot, heat the olive oil over medium heat.

Add the chopped leek and sauté until softened.

Add the diced sweet potatoes, potatoes, and carrots to the pot.

Pour in the vegetable broth and bring to a boil.

Reduce heat and simmer for 30-35 minutes, or until the vegetables are tender.

Use an immersion blender or transfer the soup to a regular blender and blend until smooth.

Season with salt and pepper to taste.

Serve hot.