In a 6-quart pan, over medium high heat, add butter and onions and cook, stirring often, until onions are limp. Add broth, carrots, and ginger. Cover and bring to a boil. Reduce heat and simmer until carrots are tender when pierced.
Remove from heat and transfer to a blender. Don't fill the blender more than half way, do it in batches if you have to. Cover the blender and then hold a kitchen towel over the top of the blender*. Be careful when blending hot liquids as the mixture can spurt out of the blender. Pulse the blender to start it and then puree until smooth. Return to the pan and add cream, stir over high heat until hot. For a smoother flavor bring soup to a boil, add salt and pepper, to taste.
Ladle into bowls and garnish with dollop sour cream and parsley sprigs.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.
When blending hot liquid, first let it cool for five minutes or so, then transfer it to a blender, filling only halfway. Put the lid on, leaving one corner open. Cover the lid with a kitchen towel to catch splatters, and pulse until smooth.