Melt 2 tablespoons butter in a saucepan. Add spelt and cook until fragrant and toasted. Deglaze with broth. Simmer over medium heat, stirring occasionally, 20-25 minutes.
Meanwhile, peel soup vegetables and cut into very small cubes. Peel and finely chop shallot. In a frying pan, heat remaining butter. Add shallot and diced vegetables and sauté 2-3 minutes. Transfer shallot and vegetable mixture to soup and simmer 5-8 minutes more. Season with salt, pepper and nutmeg.
Rinse parsley, shake dry and strip leaves from stems. Season soup and ladle into preheated soup bowls. Garnish each serving with a tablespoon of sour cream and sprinkle with parsley leaves.