Heat oil in a large saucepan over medium-high heat. Add shallots; saute in hot oil until tender, about 3 minutes.
Stir sweet potato, carrot, ginger, and curry powder together in the saucepan with the shallots; cook and stir until just beginning to soften, 3 to 4 minutes.
Pour chicken broth over the vegetable mixture; bring to a boil, cover the saucepan, reduce heat to low, and simmer until the vegetables are tender, 25 to 30 minutes. Season soup with salt.
Pour about half the soup into a blender no more than half full. Hold lid in place and pulse blender a few times before leaving on to puree. Pour pureed soup into a serving bowl and repeat with remaining soup.