I think this soup works best when it is puréed until perfectly smooth. This is best achieved using an upright blender. If you use an immersion blender, just keep working at it until the soup is as smooth as you can make it.
We use chicken stock in this recipe, but you can easily use vegetable stock for a vegetarian option.
1 Sauté onions and carrots: Melt the butter in a soup pot over medium heat and cook the onions and carrot, stirring occasionally, until the onions soften, about 5 to 8 minutes. Do not let the onions or carrots brown. Sprinkle a teaspoon of salt over the carrots and onions as they cook.
2 Add stock and water, ginger, and strips of orange zest. Bring to a simmer, cover, and cook until the carrots soften, about 20 minutes.
3 Remove the strips of orange zest and discard.
4 Purée soup: Working in small batches, pour the soup into a blender and purée until completely smooth. Only fill the blender bowl a third full with the hot liquid and keep one hand pressing down on the cap of the blender to keep it from popping off.
Add more salt to taste. (You will need more salt if you are using homemade unsalted stock or unsalted butter.)
Garnish with chopped chives, parsley, or fennel fronds.