From: Gourmet Vegetarian Feasts, by Martha Rose Shuleman, 1989.
Heat oil in a large heavy-bottomed soup pot and add onion and garlic. Saute for a couple of minutes and then add the other vegetables, dill seeds, salt and pepper. Cook, stirring, for another minute, then add water or stock. Bring to a boil, cover, reduce heat and cook for 1 hour.
Remove 2 cups from pot and puree in a blender or put through a food mill. Return to soup pot. Correct seasonings.
Serve, topping each bowl with a spoonful of yogurt.