Add the oil to a large pot on medium-high heat. Sautée the leek and onion for 10 minutes, stirring fairly often.
Stir in the garlic and cook for about 30 seconds, or until fragrant.
Add the vegetable broth, water, pumpkin purée, carrot, lentils, Italian seasoning, cumin, and chili powder. Increase heat to high and bring to a boil.
Once it's boiling, reduce heat to medium-low and cover with the lid slightly ajar. Let it simmer for 20 minutes.
Blend the soup in batches until it's smooth (I suggest letting the soup cool for at least 15 minutes first). Season with salt & pepper as needed and serve immediately.