Mix the first 4 ingredients. Using a 1-teaspoon measuring spoon, shape the mixture into 12 balls. Freeze on a waxed paper-lined baking sheet until firm. Transfer to a freezer container.
In a medium stock pot, heat oil over medium heat; sauté rutabagas, celery root, leeks, and carrot for 8 minutes. Add the garlic and cook and stir for 2 minutes. Stir in stock, herbs, salt, and pepper, and bring it to a boil. Reduce the heat; cover it and let it simmer for about 30-35 minutes or until vegetables are tender.
Cool slightly and puree the soup in batches in a blender and then return to the pan. Stir in the milk and let it heat through. Top the servings with chives and herbed margarine.
