In a medium saucepan, melt butter over medium heat. Add onion and garlic. Cook for 5 minutes, stirring frequently.
Add carrot, parsnip, and celery. Cook for 5 minutes, stirring frequently.
Add chicken broth, coriander, sugar, salt, garlic powder, and white pepper. Bring to a boil, reduce heat to medium-low, and simmer for 30 minutes. Remove from heat, and let cool slightly.
Transfer soup to a blender, and purée until smooth. Return soup to saucepan over medium heat. Add cream and sour cream, whisking until smooth. Cook until heated through, approximately 22 minutes.
Garnish individual servings with carrot curls, parsnip curls, and carrot leaves, if desired.
Recipe by TeaTime Magazine at https://teatimemagazine.com/carrot-and-parsnip-soup-recipe/