Bill Sammons purees this creamy and lightly flavored soup using a conical strainer and a wooden spoon, but we found that a blender or a food processor also gives a lovely, smooth texture.
In a good-sized stockpot, saute onions in butter until translucent; add shredded carrots and stir over medium heat until wilted (4 to 5 minutes). Add chicken stock and bring to a boil. Add rice, shallots, salt, pepper, and chervil. Simmer for 40 minutes. Puree. Return to pot and bring back to boil. Then remove from heat and add orange juice, heavy cream, and sour cream. Heat thoroughly and serve immediately, dusted with nutmeg or paprika. The soup may be served in individual bowls or cups, each with its own dollop of sour cream.