2 tablespoons olive oil
2 medium onions, roughly chopped
1 pound carrots, roughly chopped
1 large sweet potato (about 3/4 pound), roughly chopped
2 rounded teaspoons freshly minced ginger
1/2 kosher salt
4 cups water or broth
2 tablespoons butter or olive oil
Heavy cream, for garnish
Green onions, chopped, for garnish
In a stockpot, heat oil over medium-high heat. When oil is hot but not smoking, add onions. Cook, stirring frequently, until onions are soft and translucent (about 5 to 7 minutes).
Add carrots, sweet potato, ginger and salt; stir for an additional 2 to 3 minutes. Add water or broth and bring to a boil. Reduce heat to low, cover, and simmer until vegetables are very soft (about 15 minutes).
Using an immersion blender (or in batches in a countertop blender or food processor), purée the soup until smooth. Stir in butter or olive oil. Taste, and add additional salt if needed. Ladle soup into serving bowls and garnish with a swirl of heavy cream and a sprinkle of green onions.