Heat the olive oil in a large stock pot over medium heat. Add the onion, ginger and garlic and cook for 5 minutes or until the onions soften, stirring often.
Add the carrots, chicken stock, water, bay leaves, thyme sprigs and salt and pepper. Bring to a boil then reduce to simmer and cook until the carrots are tender, about 35-40 minutes.
Remove the bay leaves and thyme sprigs and blend the mixture with an immersion blender or transfer to a blender and blend until smooth. Blend in the vanilla yogurt and butter and season with more salt and white pepper to taste.
Serve with a dollop of yogurt and fresh thyme if desired.
Notes
*If you use chicken broth rather than the stronger, concentrated chicken stock, replace 2 of the cups of water with the broth.