Peel the sweet potato and cut it into bite-sized chunks. Peel and chop the carrots, celery and onion.
Cook the vegetables in olive oil over medium heat in a large pan until they are slightly browned.
Pour them into a large pot and add enough broth to cover them. Bring the mixture to a boil.
Turn down the heat and simmer for 5 ľ 10 minutes until the vegetables are tender.
Pour the mixture in a blender and blend until you get a creamy consistency. Return soup to the pot; add salt and pepper to taste and heat the soup back up.