Add vegetable oil to a large pot over medium heat. Add the onion, ginger and garlic. Cook, stirring frequently, until onions are soft.
Add the carrots and potatoes to the pot. Cook until the carrots start to sweat.
Add broth and bring to gentle boil.
Simmer, covered for 25 to 30 minutes or until carrots and potatoes are cooked.
Remove from heat and let cool for 15 minutes. Transfer carrots and ½ the potatoes to blender. Pour in half your broth and purée soup (be sure to let steam escape).
Add sour cream and blend well.
Continue adding broth until desired thickness. Season with salt and pepper.
Add extra potatoes to soup and garnish with green onions and Italian parsley.