1. Melt butter in large saucepan or dutch oven and saute onions and garlic until soft. If you are looking to reduce calories you can saute them in a little broth instead.
2. Add broth, carrots, and ginger and bring to a boil. Reduce heat and simmer until carrots are soft, about 20-30 minutes.
3. Add sour cream, if desired, and then blend soup with immersion blend or transfer to blender if necessary. Adjust salt and pepper to taste.