1. Melt butter in large saucepan over medium heat. Add onions, crystallized ginger, fresh ginger, garlic, 2 teaspoons salt, and sugar; cook, stirring frequently, until onions are softened but not browned, 5 to 7 minutes.

2. Increase heat to high; add carrots, water, 3/4 cup carrot juice, thyme sprigs, and baking soda and bring to simmer. Reduce heat to medium-low and simmer, covered, until carrots are very tender, 20 to 25 minutes.

3. Discard thyme sprigs. Working in batches, process soup in blender until smooth, 1 to 2 minutes. Return soup to clean pot and stir in vinegar and remaining 3/4 cup carrot juice. (Soup can be refrigerated for up to 4 days.) Return to simmer over medium heat and season with salt and pepper to taste. Serve with sprinkle of chives and dollop of sour cream.

Serves 6