Saute the onion and garlic in a small amount of olive oil until soft. Add the sweet potatoes and carrots and stir to combine. Mix in the curry paste and cook for 1 minute, until fragrant. Add the vegetable broth. Bring to a boil, lower the heat, and simmer, covered, until the sweet potatoes and carrots are softened, about 20 minutes. Using an immersion blender or carefully using a blender, blend until smooth. Season with salt and pepper and serve hot. Garnish with chopped cilantro or a drizzle of cream, if you wish. I did neither. Some crunchy croutons or oyster crackers would also be excellent.
Recipe by Katherine Martinelli at http://www.katherinemartinelli.com/blog/recipe/2011/sweet-potato-soup-with-attitude/