Heat chicken stock in a large saucepan over medium heat. Place 4 cups vegetable mixture in the bowl of a food processor. Add stock, 1 cup at a time, processing after each addition until smooth. Add soup to saucepan; simmer 2 minutes. Stir in sour cream, vinegar, salt, ground red pepper, and nutmeg. Place 1 1/2 cups soup in each of 4 bowls; top each serving with 1 cooked and crumbled bacon slice and 1 teaspoon chopped parsley.